Temporarily remove the Android on Mac test runs

[a-maurice]

Description

Provide details of the change, and generalize the change in the PR title above.

The GHA machines have been giving errors on Mac when trying to build the Android testapps, primarily around NDK and JDK issues. Disable these tests for now, until we can track down the root cause of the issue.

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Testing

Describe how you've tested these changes.

https://github.com/firebase/firebase-unity-sdk/actions/runs/8760959333

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Type of Change

Place an x the applicable box:

• Bug fix. Add the issue # below if applicable.
• New feature. A non-breaking change which adds functionality.
• Other, such as a build process or documentation change.

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