Add a Doxygen filter for .h files (backport #523)

[mergify]

🦟 Bug fix

Summary

Doxygen can not parse the GZ_DEPRECATED() macro in a .h file because the existing filter pattern was only applied to *.hh files, not *.h files.

Here's an example without this patch:

And with this patch:

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
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This is an automatic backport of pull request #523 done by Mergify.