Remove symlink to audio_effects_conf.xsd

A change is being made so that sandboxed genrules need to add a
dependency on the targets of the symlinks they use.

In this case, the symlink isn't necessary, and we can just depend
on the audio_effects_conf_V2_0 genrule instead.

Bug: 307824623
Test: m audio_effects_conf_V4_0
Change-Id: I6ddaa81e08d7c4a9c29412b11a08f1d6b88689b5