Description of problem:
Installing libavcodec-freeworld doesn't cause GStreamer to "notice" H.264 playback capability.

Version-Release number of selected component (if applicable):
gstreamer1-plugin-libav-1.22.8-1.fc38.x86_64

How reproducible:
Always

Steps to Reproduce:
1 Ensure only libavcodec-free is installed and not hardware decoding is available:
  dnf remove libavcodec-freeworld ffmpeg-libs gstreamer1-plugin-openh264 gstreamer1-plugins-bad-free
2. rm .cache/gstreamer-1.0/registry.*.bin
3. Try playing a H.264 video using e.g. clapper
-> black image
4. Install libavcodec-freeworld
5. Try playing H.264 video again
-> still black image
6. rm .cache/gstreamer-1.0/registry.*.bin
7. Try playing H.264 video again
-> plays fine

Actual results:
With gstreamer1-plugin-libav and libavcodec-free (no H.264 decoding capability) installed, installing libavcodec-freeworld doesn't cause GStreamer to notice it can play H.264 now and the video stream is missing (black) until user gstreamer plugin cache is rebuilt.

Expected results:
H.264 playback works immediately after installing libavcodec-freeworld, without manually removing gstreamer plugin cache.

Additional info:
This was reported on Discourse: https://discussion.fedoraproject.org/t/totem-h-265-no-video-only-audio-problem/100818/2 .