audio/{speex|speexdsp}: Update to upstream release 1.2.1
Details:
- Despite speex is officially obsoleted by Opus (see banner on https://speex.org/), there have been multiple fixes over the years since the 1.2.0 release, including cleanups and potential overflows detected via fuzzing. Details: https://gitlab.xiph.org/xiph/speex/-/commits/release/1.2.1/ https://gitlab.xiph.org/xiph/speexdsp/-/commits/release/1.2.1/