[google_sign_in] use Object in operator == for mocking

[evan361425]

When using mockito for GoogleSignInAccount, the static analyzer starts complaint:

'Mock.==' ('bool Function(Object)') isn't a valid concrete implementation of 'GoogleSignInAccount.==' ('bool Function(dynamic)').

Which means it should be Object in the operator =='s argument.

Fixed issues:

• plugin(google_sign_in): use Object type for GoogleSignInAccount operator flutter#104378

no changes in flutter/tests repo.

Test

As I read the suggestion: is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

I'm not sure how to add the test to prevent revert changing, any testing tips for this kind of fixes?

Pre-launch Checklist

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• I signed the CLA.
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• I listed at least one issue that this PR fixes in the description above.
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If you need help, consider asking for advice on the #hackers-new channel on Discord.

[flutter-dashboard]

It looks like this pull request may not have tests. Please make sure to add tests before merging. If you need an exemption to this rule, contact Hixie on the #hackers channel in Chat (don't just cc him here, he won't see it! He's on Discord!).

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing.

[evan361425]

duplicate with #5642