[ios] Correct host os version for iOS 12 tests.

Limit to 10.13.4 or 10.13.5.

NOTRY=true

Bug: 843236
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I4319717afc3ad7d8fa64e2276c3b877d5f7b6837
Reviewed-on: https://chromium-review.googlesource.com/1089037
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Reviewed-by: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#564908}

ios/build/bots/chromium.fyi/ios12-sdk-simulator.json

@@ -29,6 +29,10 @@
         {
           "os": "Mac-10.13.4",
           "pool": "Chrome"
+        },
+        {
+          "os": "Mac-10.13.5",
+          "pool": "Chrome"
         }
       ]
     },
@@ -40,6 +44,10 @@
         {
           "os": "Mac-10.13.4",
           "pool": "Chrome"
+        },
+        {
+          "os": "Mac-10.13.5",
+          "pool": "Chrome"
         }
       ]
     },
@@ -51,6 +59,10 @@
         {
           "os": "Mac-10.13.4",
           "pool": "Chrome"
+        },
+        {
+          "os": "Mac-10.13.5",
+          "pool": "Chrome"
         }
       ]
     },
@@ -62,6 +74,10 @@
         {
           "os": "Mac-10.13.4",
           "pool": "Chrome"
+        },
+        {
+          "os": "Mac-10.13.5",
+          "pool": "Chrome"
         }
       ]
     },
@@ -185,6 +201,10 @@
         {
           "os": "Mac-10.13.4",
           "pool": "Chrome"
+        },
+        {
+          "os": "Mac-10.13.5",
+          "pool": "Chrome"
         }
       ]
     },
@@ -196,6 +216,10 @@
         {
           "os": "Mac-10.13.4",
           "pool": "Chrome"
+        },
+        {
+          "os": "Mac-10.13.5",
+          "pool": "Chrome"
         }
       ]
     },
@@ -207,6 +231,10 @@
         {
           "os": "Mac-10.13.4",
           "pool": "Chrome"
+        },
+        {
+          "os": "Mac-10.13.5",
+          "pool": "Chrome"
         }
       ]
     },
@@ -250,6 +278,10 @@
         {
           "os": "Mac-10.13.4",
           "pool": "Chrome"
+        },
+        {
+          "os": "Mac-10.13.5",
+          "pool": "Chrome"
         }
       ]
     },
@@ -293,6 +325,10 @@
         {
           "os": "Mac-10.13.4",
           "pool": "Chrome"
+        },
+        {
+          "os": "Mac-10.13.5",
+          "pool": "Chrome"
         }
       ]
     },

ios/build/bots/chromium.mac/ios12-sdk-simulator.json

 {
   "comments": [
-    "Runs tests on 64-bit iOS 10 and 11 and 12 tests",
+    "Runs tests on 64-bit iOS 10.3 and 11.2 and 12.0 tests",
     "on iPad, iPhone, @3x, and @2x on main and CQ ios12-beta-simulator.",
     "Note: Xcode 10.3 requires Mac OS 10.13.X or higher, hence 'host os'."
   ],
@@ -27,7 +27,11 @@
       "os": "12.0",
       "dimensions": [
         {
-          "os": "Mac-10.13",
+          "os": "Mac-10.13.4",
+          "pool": "Chrome"
+        },
+        {
+          "os": "Mac-10.13.5",
           "pool": "Chrome"
         }
       ]
@@ -38,7 +42,11 @@
       "os": "12.0",
       "dimensions": [
         {
-          "os": "Mac-10.13",
+          "os": "Mac-10.13.4",
+          "pool": "Chrome"
+        },
+        {
+          "os": "Mac-10.13.5",
           "pool": "Chrome"
         }
       ]
@@ -49,7 +57,11 @@
       "os": "12.0",
       "dimensions": [
         {
-          "os": "Mac-10.13",
+          "os": "Mac-10.13.4",
+          "pool": "Chrome"
+        },
+        {
+          "os": "Mac-10.13.5",
           "pool": "Chrome"
         }
       ]
@@ -60,7 +72,11 @@
       "os": "12.0",
       "dimensions": [
         {
-          "os": "Mac-10.13",
+          "os": "Mac-10.13.4",
+          "pool": "Chrome"
+        },
+        {
+          "os": "Mac-10.13.5",
           "pool": "Chrome"
         }
       ]
@@ -183,7 +199,11 @@
       "os": "12.0",
       "dimensions": [
         {
-          "os": "Mac-10.13",
+          "os": "Mac-10.13.4",
+          "pool": "Chrome"
+        },
+        {
+          "os": "Mac-10.13.5",
           "pool": "Chrome"
         }
       ]
@@ -194,7 +214,11 @@
       "os": "12.0",
       "dimensions": [
         {
-          "os": "Mac-10.13",
+          "os": "Mac-10.13.4",
+          "pool": "Chrome"
+        },
+        {
+          "os": "Mac-10.13.5",
           "pool": "Chrome"
         }
       ]
@@ -205,7 +229,11 @@
       "os": "12.0",
       "dimensions": [
         {
-          "os": "Mac-10.13",
+          "os": "Mac-10.13.4",
+          "pool": "Chrome"
+        },
+        {
+          "os": "Mac-10.13.5",
           "pool": "Chrome"
         }
       ]
@@ -248,7 +276,11 @@
       "os": "12.0",
       "dimensions": [
         {
-          "os": "Mac-10.13",
+          "os": "Mac-10.13.4",
+          "pool": "Chrome"
+        },
+        {
+          "os": "Mac-10.13.5",
           "pool": "Chrome"
         }
       ]
@@ -291,7 +323,11 @@
       "os": "12.0",
       "dimensions": [
         {
-          "os": "Mac-10.13",
+          "os": "Mac-10.13.4",
+          "pool": "Chrome"
+        },
+        {
+          "os": "Mac-10.13.5",
           "pool": "Chrome"
         }
       ]