testing/noise-supression-for-voice: Fix lv2 install location and disable VST

lv2 lib now installed in the correct location (/usr/lib/lv2/rnnoise.lv2) and it now also include the missing .ttl files.

Previously this was logged when starting Easyeffects: error: failed to open file /usr/lib/lv2/librnnoise_lv2.so/manifest.ttl (Not a directory) lilv_world_load_file(): error: Error loading file `file:///usr/lib/lv2/librnnoise_lv2.so/manifest.ttl' lilv_world_load_bundle(): error: Error reading file:///usr/lib/lv2/librnnoise_lv2.so/manifest.ttl

Building of the VST plugin has been disabled since it was not built anyway, but it produced warnings in the build log...