chore: only commit schema changes when actually changed

[byCedric]

Linked issue

This should minimize the amount of "failure" in the schema workflows.

Additional context

Copied from https://github.com/expo/expo-github-action/commit/ee415b027afce4c15cabcc6fa2f8368530a36c08

Tested workflows:

• schema-eas-metadata - https://github.com/expo/vscode-expo/actions/runs/2796479961
• schema-expo-xdl - https://github.com/expo/vscode-expo/actions/runs/2796481842

[github-actions[bot]]

:tada: This PR is included in version 0.8.1 :tada:

The release is available on GitHub release

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