[ios] Test one shard on ios13 sdk-simulator bot.

Also fixes missing shard:1 on chromium.mac.

Change-Id: If42a81850eac21afee5dd737bbd7c4030b06189a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1715422
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Commit-Queue: Rohit Rao <rohitrao@chromium.org>
Auto-Submit: Justin Cohen <justincohen@chromium.org>
Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#680585}

ios/build/bots/chromium.fyi/ios13-sdk-simulator.json

@@ -58,6 +58,7 @@
       "priority": 30
     },
     {
+      "shards": 1,
       "include": "eg_tests.json",
       "device type": "iPhone 7",
       "os": "13.0",
@@ -71,6 +72,7 @@
       "priority": 30
     },
     {
+      "shards": 1,
       "include": "eg_tests.json",
       "device type": "iPad Air 2",
       "os": "13.0",
@@ -84,6 +86,7 @@
       "priority": 30
     },
     {
+      "shards": 1,
       "include": "eg_tests.json",
       "device type": "iPhone X",
       "os": "13.0",
@@ -97,6 +100,7 @@
       "priority": 30
     },
     {
+      "shards": 1,
       "include": "eg_cq_tests.json",
       "device type": "iPhone X",
       "os": "13.0",
@@ -110,6 +114,7 @@
       "priority": 30
     },
     {
+      "shards": 1,
       "include": "eg_cq_tests.json",
       "device type": "iPad Air 2",
       "os": "13.0",

ios/build/bots/chromium.mac/ios13-beta-simulator.json

@@ -89,6 +89,7 @@
       }
     },
     {
+      "shards": 1,
       "include": "eg_cq_tests.json",
       "device type": "iPhone X",
       "os": "13.0",
@@ -102,6 +103,7 @@
       }
     },
     {
+      "shards": 1,
       "include": "eg_cq_tests.json",
       "device type": "iPad Pro (12.9-inch)",
       "os": "13.0",
@@ -115,6 +117,7 @@
       }
     },
     {
+      "shards": 1,
       "include": "eg_tests.json",
       "device type": "iPhone X",
       "os": "13.0",
@@ -128,6 +131,7 @@
       }
     },
     {
+      "shards": 1,
       "include": "eg_tests.json",
       "device type": "iPad Air (3rd generation)",
       "os": "13.0",

ios/build/bots/chromium.mac/ios13-sdk-simulator.json

@@ -61,6 +61,7 @@
       "priority": 30
     },
     {
+      "shards": 1,
       "include": "eg_tests.json",
       "device type": "iPhone 7",
       "os": "13.0",
@@ -74,6 +75,7 @@
       "priority": 30
     },
     {
+      "shards": 1,
       "include": "eg_tests.json",
       "device type": "iPad Air 2",
       "os": "13.0",
@@ -87,6 +89,7 @@
       "priority": 30
     },
     {
+      "shards": 1,
       "include": "eg_tests.json",
       "device type": "iPhone X",
       "os": "13.0",
@@ -100,6 +103,7 @@
       "priority": 30
     },
     {
+      "shards": 1,
       "include": "eg_cq_tests.json",
       "device type": "iPhone X",
       "os": "13.0",
@@ -113,6 +117,7 @@
       "priority": 30
     },
     {
+      "shards": 1,
       "include": "eg_cq_tests.json",
       "device type": "iPad Air 2",
       "os": "13.0",