vaapidecode: remove extraneous size information from allowed caps.

Fix _getcaps() implementation to not report codecs with size information
filled in the returned caps. That's totally useless nowadays. Ideally,
this is a hint to insert a video parser element, thus allowing future
optimizations, but this is not a strict requirement for gstreamer-vaapi,
which is able to parse the elementary bitstreams itself.

https://bugzilla.gnome.org/show_bug.cgi?id=704734

gst/vaapi/gstvaapidecode.c

@@ -814,12 +814,6 @@ gst_vaapidecode_ensure_allowed_caps(GstVaapiDecode *decode)
         if (!structure)
             continue;
         gst_structure_remove_field(structure, "profile");
-        gst_structure_set(
-            structure,
-            "width",  GST_TYPE_INT_RANGE, 1, G_MAXINT,
-            "height", GST_TYPE_INT_RANGE, 1, G_MAXINT,
-            NULL
-        );
         decode->allowed_caps =
             gst_caps_merge_structure(decode->allowed_caps, structure);
     }