Skip Xcode install on mac_mokey Android tests (#163685)

These tests are failing on querying Xcode for simulator devices when
running Android tests. Ideally recipes wouldn't try to install Xcode
unless requested via `"sdk_version": "[xcode version number]"` property,
[but they do](flutter/flutter#163670). Since
the recipe[ mapping of macOS version to Xcode
version](https://flutter.googlesource.com/recipes/+/refs/heads/main/recipe_modules/osx_sdk/api.py#22)
is out of date, it's falling back to an old version of Xcode when none
are specified.

Stop installing Xcode on these builder configurations. If this works
I'll follow up and add it to `mac_pixel_7pro`, `mac_arm64_android`, etc.

First step of flutter/flutter#161655. If this
works `bringup` can be removed.
Fixes flutter/flutter#163309

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there for submitting PRs.
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responsibilities.
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we expect every widget to implement].
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- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] All existing and new tests are passing.

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on [Discord].

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Author: jmagman

.ci.yaml

@@ -252,6 +252,10 @@ platform_properties:
       os: Mac-13|Mac-14
       cpu: x86
       device_type: "mokey"
+      $flutter/osx_sdk : >-
+        {
+          "skip_xcode_install": true
+        }
   mac_arm64_mokey:
     properties:
       dependencies: >-
@@ -262,6 +266,10 @@ platform_properties:
       os: Mac-13|Mac-14
       cpu: arm64
       device_type: "mokey"
+      $flutter/osx_sdk : >-
+        {
+          "skip_xcode_install": true
+        }
 
   mac_pixel_7pro:
     properties: