Serve .flac audio files

[SystemKeeper]

Summary

To support call sounds in Safari we need to use *.flac audio files, since *.ogg is not supported by Safari (nextcloud/spreed#9422). But currently *.flac files will not be served, so

https://.../apps/spreed/img/join_call.ogg -> works
https://.../apps/spreed/img/join_call.flac -> does not work

Since we added call sounds with 27, backport to stable27?

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[nickvergessen]

Please also update the nginx docs:
https://docs.nextcloud.com/server/stable/admin_manual/installation/nginx.html

    # Serve static files
    location ~ \.(?:css|js|mjs|svg|gif|png|jpg|ico|wasm|tflite|map)$ {

And add to https://docs.nextcloud.com/server/stable/admin_manual/release_notes/upgrade_to_27.html

[nickvergessen]

/backport to stable27

[SystemKeeper]

Please also update the nginx docs:

Done in nextcloud/documentation#11288