ALSA: emu10k1: de-duplicate audigy-mixer.rst vs. sb-live-mixer.rst

Let the MANUALS/PATENTS section of the former simply refer to the latter
- there is no point in duplicating this information with little value to
end users.

Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Link: https://lore.kernel.org/r/20230825222157.170978-1-oswald.buddenhagen@gmx.de


Signed-off-by: Takashi Iwai <tiwai@suse.de>