Add "record:no" to the Raspberry Pi section of the readme

[antisaint81]

Describe the feature

Fairly new to mediamtx but love it, thanks for this.

In the readme for RPI, it explains how to add the option to use a microphone:

_paths:
cam:
source: rpiCamera

cam_with_audio:
runOnInit: >
gst-launch-1.0
rtspclientsink name=s location=rtsp://localhost:$RTSP_PORT/cam_with_audio
rtspsrc location=rtsp://127.0.0.1:$RTSP_PORT/cam latency=0 ! rtph264depay ! s.
alsasrc device=default:CARD=U0x46d0x809 ! opusenc bitrate=16000 ! s.
runOnInitRestart: yes_

However if recording is turned on, it records a the stream from both paths, leading to two videos, one with sound, one without.

Adding "record:no" to the cam source as shown below

paths:
cam:
source: rpiCamera
record:no

Will prevent the server from recording from the video-only source. I'm not sure if this is clarified somewhere and I missed it, but it might be helpful to add that info. Thanks!