Append acquired_caps to the filter_caps being built, instead of a 2nd copy of acquired_drm_caps. Fix a regression introduced in https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/7633 when downstream doesn't support DRM output. Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8385>