This broke in 81bdef0150df3306136137a5187dc25a7c5f4aee. Simplify
removal of the plugin from the plugin list if features are listed, and
fix invocation of the script -- it was adding an extra space before
the first plugin filename.
Also ensure that gst-full CI is run when the script changes.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/9452>