taglist: Remove (scope call) annotation from gst_tag_register()
This was added in 7fdb15d6 but it is wrong. (scope call) is for closures that only have to stay valid for the scope of the call, but the tag merge function has to stay valid for the whole lifetime of the application instead.
There's no appropriate scope annotation for that so we have to skip these functions for now.
CC @ndufresne who added the annotation in the first place.