LibAudio: Update FlacLoader comments and links to RFC 9639

[Kenxpx]

LibAudio: Update FlacLoader comments and links to RFC 9639

Updated all references to FLAC specifications within FlacLoader.h and FlacLoader.cpp to point to the official RFC 9639. This includes updating section numbers, direct links, and notes about previously referenced draft specifications.

Fixes #25825.

[LucasChollet]

@kleinesfilmroellchen you probably want to give it a look

[nico]

You need to run clang-format, see CI results.

[Kenxpx]

i ran clang-format but it still giving me same errors

[stale[bot]]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs. Thank you for your contributions!

[stale[bot]]

This pull request has been closed because it has not had recent activity. Feel free to re-open if you wish to still contribute these changes. Thank you for your contributions!