community/webrtc-audio-processing-2: upgrade to 2.1

Upstream versioned their packages because they can't promise keeping the API stable, so I believe keeping the versioning downstream makes sense too.

Ref: https://gitlab.freedesktop.org/pulseaudio/webrtc-audio-processing/-/commit/21d78a4267017b2beafbe33c03faab3f22b02a18 Changelog: https://gitlab.freedesktop.org/pulseaudio/webrtc-audio-processing/-/blob/v2.1/NEWS