www/*nginx: Switch nginx-vod-module to maintained fork

The original Kaltura nginx-vod-module repository is no longer actively
maintained and has been incompatible with FFmpeg 8 due to removed
legacy API calls.

Switch to the actively maintained fork:
https://github.com/diogoazevedos/nginx-vod-module

This restores compatibility with newer FFmpeg versions.

Reported by: Jim Terhune via ML
Sponsored by: Netzkommune GmbH