Docs: FFmpeg plugin docs - ST30 PCM16 audio demuxer

[MateuszGrabuszynski]

Fixes an error with -f parameter for receiving PCM16 audio via an FFmpeg plugin (-f mtl_st30p_pcm16 to -f mtl_st30p).

[DawidWesierski4]

This edit is for the muuuxer :(

[DawidWesierski4]

[labrat@localhost FFmpeg]$ ffmpeg -p_port $VFIO_PORT_T -p_sip 192.168.96.2 -p_rx_ip 239.168.85.20 -udp_port 30000 -payload_type 97 -pcm_fmt pcm16 -ptime 1ms -channels 2 -f mtl_st30p_pcm16 -i "0" dump_pcm16.wav -y
ffmpeg version n7.0.2-35-g5d9a2c97b8 Copyright (c) 2000-2024 the FFmpeg developers
built with gcc 11 (GCC)
configuration: --enable-shared --disable-static --enable-nonfree --enable-pic --enable-gpl --enable-libopenh264 --enable-encoder=libopenh264 --enable-mtl --enable-debug
libavutil 59. 8.100 / 59. 8.100
libavcodec 61. 3.100 / 61. 3.100
libavformat 61. 1.100 / 61. 1.100
libavdevice 61. 1.100 / 61. 1.100
libavfilter 10. 1.100 / 10. 1.100
libswscale 8. 1.100 / 8. 1.100
libswresample 5. 1.100 / 5. 1.100
libpostproc 58. 1.100 / 58. 1.100
[in#0 @ 0x620c00] Unknown input format: 'mtl_st30p_pcm16'
Error opening input file 0.
Error opening input files: Invalid argument

this RX is where there is the issue

[DawidWesierski4]

Lovly lgtm