rgb-matrix.sh: Update disabling sound for quality mod for RGB matrix HAT

[rohithm8]

This script allows selection between two different pinouts corresponding to the quality mod (soldering a wire between gpio 4-18) and the unaltered HAT. However, the quality mod requires disabling onboard sound. Although the method in rgb-matrix.sh worked for older versions of Raspbian, for the latest Raspberry Pi OS I think that it is necessary to blacklist it in the kernel (as commented in the script). Perhaps something like:
sudo echo -n "blacklist snd_bcm2835" > /etc/modprobe.d/alsa-blacklist.conf
will do the job.

Reference to where this issue is:
https://github.com/adafruit/Raspberry-Pi-Installer-Scripts/blob/339cccfbdd8b503b53186176ff96bead9a13a2f5/rgb-matrix.sh#L276C1-L278C69

Thank you for providing this resource - it has made it significantly easier to use this HAT!