gstreamer1: updated to 1.20.4

Highlighted bugfixes in 1.20.4

avaudiodec: fix playback issue with WMA files, would throw an error at EOS with FFmpeg 5.x
Fix deadlock when loading gst-editing-services plugin
Fix input buffering capacity in live mode for aggregator, video/audio aggregator subclasses, muxers
glimagesink: fix crash on Android
subtitle handling and subtitle overlay fixes
matroska-mux: allow width + height changes for avc3|hev1|vp8|vp9
rtspsrc: fix control url handling for spec compliant servers and add fallback for incompliant servers
WebRTC fixes
RTP retransmission fixes
video: fixes for formats with 4x subsampling and horizontal co-sited chroma (Y41B, YUV9, YVU9 and IYU9)
macOS build and packaging fixes, in particular fix finding of gio modules on macOS for https/TLS support
Fix consuming of the macOS package as a framework in XCode
Performance improvements
Miscellaneous bug fixes, memory leak fixes, and other stability and reliability improvements

(adam)