[4.2] Code style for webauthn plugin

[heelc29]

Summary of Changes

Code style for changes in #37910

Testing Instructions

Code review

[richard67]

I have tested this item ✅ successfully on a0054c2

Ok by review, and code style checks still succeed in drone.

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[Quy]

I have tested this item ✅ successfully on a0054c2

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[Quy]

RTC

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[richard67]

@HLeithner Any idea why PHPCS doesn't complain about the code style in that file without this PR?

[laoneo]

Thanks!