rtp/hdrext: correct gst_rtp_get_header_extension_list() docs
The return value is a list of GstElementFactory's that when gst_element_factory_create()ed will create a GstRTPHeaderExtension.
Fixes #897 (closed)
The return value is a list of GstElementFactory's that when gst_element_factory_create()ed will create a GstRTPHeaderExtension.
Fixes #897 (closed)