[Cherrypick] Fix repeat events of modifier keys on Windows

[dkwingsmt]

Cherrypick https://github.com/flutter/engine/pull/35046

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• [ ] I read the Contributor Guide and followed the process outlined there for submitting PRs.
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• [ ] I listed at least one issue that this PR fixes in the description above.
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• [ ] All existing and new tests are passing.

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