Disable the other new Messaging test on Desktop

[a-maurice]

Description

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

The other new Messaging test will also have problems on Desktop because of the stubbed out implementation, so disable it.

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Testing

Describe how you've tested these changes. Link any manually triggered Integration tests or CPP binary SDK Packaging Github Action workflows, if applicable.

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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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Notes

• Bug fixes and feature changes require an update to the Release Notes section of release_build_files/readme.md.
• Read the contribution guidelines CONTRIBUTING.md.
• Changes to the public API require an internal API review. If you'd like to help us make Firebase APIs better, please propose your change in a feature request so that we can discuss it together.

[gemini-code-assist]

Code Review

This pull request updates the integration test TestRegistrationOnInitEnabled in messaging/integration_test/src/integration_test.cc to skip execution on desktop and Android emulator environments. There are no review comments, so I have no feedback to provide.