Fix capitalization of AudioRecorderWrapper and AudioPlayerWrapper in audio_doc documentation

[traversaro]

Originally reported by @giotherobot .

[update-docs]

Thanks for opening this pull request! The maintainers of this repository would appreciate it if you would update the release notes by adding a file in doc/release/<target_branch>, based on your changes.

[codacy-production]

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Coverage variation	Diff coverage
✅ +0.00%	✅ ∅

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (468e609)	112291	61384	54.67%
Head commit (1e1607e)	112291 (+0)	61386 (+2)	54.67% (+0.00%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#3141)	0	0	∅ (not applicable)

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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