ao_pipewire: avoid setting any media.role

By default, WirePlumber restores the volume of each application to
whatever the last application with the same media role used. This is
completely insane behavior, and I couldn’t find any way for a user to
opt out of it on my end. The `state-stream.lua` script responsible for
this mess only uses media.role if the property is present, so the only
reliable workaround is simply not to set one at all.

Author: llyyr

audio/out/ao_pipewire.c

@@ -577,7 +577,6 @@ static int init(struct ao *ao)
     struct pw_properties *props = pw_properties_new(
         PW_KEY_MEDIA_TYPE, "Audio",
         PW_KEY_MEDIA_CATEGORY, "Playback",
-        PW_KEY_MEDIA_ROLE, ao->init_flags & AO_INIT_MEDIA_ROLE_MUSIC ?  "Music" : "Movie",
         PW_KEY_NODE_NAME, ao->client_name,
         PW_KEY_NODE_DESCRIPTION, ao->client_name,
         PW_KEY_APP_NAME, ao->client_name,