GstVideoMeta fixed-size arrays arguments are not properly documented

See documentation of gst_buffer_add_video_meta_full(), gst_video_meta_get_plane_height() and gst_video_meta_get_plane_size(): https://gstreamer.freedesktop.org/documentation/video/gstvideometa.html

stride and offset arguments are shown as gsize * offset while the old gtk-doc shows them as gsize offset[GST_VIDEO_MAX_PLANES]. There is thus no indication that those arrays must be fixed size, giving smaller array (e.g. the actual n_planes value) crash.

gst_video_meta_get_plane_height/size() are also missing (array fixed-size=4) annotation.