Fix iOS version targeted for screen size tests.

Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I5953a6d5c0256bcf37cc8038effb7f7ca65f2a55
Reviewed-on: https://chromium-review.googlesource.com/1107280Reviewed-by: Justin Cohen <justincohen@chromium.org>
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568695}

ios/build/bots/chromium.fyi/ios11-beta-simulator.json

@@ -52,77 +52,37 @@
     {
       "include": "screen_size_dependent_tests.json",
       "device type": "iPad Air 2",
-      "os": "12.0",
-      "dimensions": [
-        {
-          "os": "Mac-10.13.4",
-          "pool": "Chrome"
-        },
-        {
-          "os": "Mac-10.13.5",
-          "pool": "Chrome"
-        }
-      ]
+      "os": "11.4",
+      "host os": "Mac-10.13",
+      "xcode build version": "9q1019a"
     },
     {
       "include": "screen_size_dependent_tests.json",
       "device type": "iPhone 5s",
-      "os": "12.0",
-      "dimensions": [
-        {
-          "os": "Mac-10.13.4",
-          "pool": "Chrome"
-        },
-        {
-          "os": "Mac-10.13.5",
-          "pool": "Chrome"
-        }
-      ]
+      "os": "11.4",
+      "host os": "Mac-10.13",
+      "xcode build version": "9q1019a"
     },
     {
       "include": "screen_size_dependent_tests.json",
       "device type": "iPhone 6s",
-      "os": "12.0",
-      "dimensions": [
-        {
-          "os": "Mac-10.13.4",
-          "pool": "Chrome"
-        },
-        {
-          "os": "Mac-10.13.5",
-          "pool": "Chrome"
-        }
-      ]
+      "os": "11.4",
+      "host os": "Mac-10.13",
+      "xcode build version": "9q1019a"
     },
     {
       "include": "screen_size_dependent_tests.json",
       "device type": "iPhone 6s Plus",
-      "os": "12.0",
-      "dimensions": [
-        {
-          "os": "Mac-10.13.4",
-          "pool": "Chrome"
-        },
-        {
-          "os": "Mac-10.13.5",
-          "pool": "Chrome"
-        }
-      ]
+      "os": "11.4",
+      "host os": "Mac-10.13",
+      "xcode build version": "9q1019a"
     },
     {
       "include": "screen_size_dependent_tests.json",
       "device type": "iPhone X",
-      "os": "12.0",
-      "dimensions": [
-        {
-          "os": "Mac-10.13.4",
-          "pool": "Chrome"
-        },
-        {
-          "os": "Mac-10.13.5",
-          "pool": "Chrome"
-        }
-      ]
+      "os": "11.4",
+      "host os": "Mac-10.13",
+      "xcode build version": "9q1019a"
     }
   ]
 }