Binding ToTiOS and ToTiOSDevice to os 10.14

The filtered (by dimensions) pool for ToTiOS* has one bot
 that is on Mac 10.13 (build227-m9), causing infra failures.
 Binding ToTiOS* bots to min required os version (10.14)
 until all bots have been upgraded.

Change-Id: I42902d6f880dff1c7d2b245e65c3ff339e645d29
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1894306Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: Jeff Yoon <jeffyoon@chromium.org>
Cr-Commit-Position: refs/heads/master@{#711869}

infra/config/buckets/ci.star

@@ -654,7 +654,7 @@ def clang_ios_builder(*, name, **kwargs):
       caches = [XCODE_IOS_11_CACHE],
       cores = None,
       executable = luci.recipe(name = 'ios/unified_builder_tester'),
-      os = os.MAC_ANY,
+      os = os.MAC_10_14,
       ssd = True,
   )
 

infra/config/generated/cr-buildbucket.cfg

@@ -5514,7 +5514,7 @@ buckets: <
       swarming_tags: "vpython:native-python-wrapper"
       dimensions: "builderless:1"
       dimensions: "cpu:x86-64"
-      dimensions: "os:Mac"
+      dimensions: "os:Mac-10.14"
       dimensions: "ssd:1"
       recipe: <
         name: "ios/unified_builder_tester"
@@ -5538,7 +5538,7 @@ buckets: <
       swarming_tags: "vpython:native-python-wrapper"
       dimensions: "builderless:1"
       dimensions: "cpu:x86-64"
-      dimensions: "os:Mac"
+      dimensions: "os:Mac-10.14"
       dimensions: "ssd:1"
       recipe: <
         name: "ios/unified_builder_tester"