rtpdiscovercodecs: Remove duplicate codecs
rtpdiscovercodecs: Remove duplicate codecs

Only keep the first codec if there is more than one way to produce
the same RTP codec

pexip/farstream,kakaroto/farstream,kakaroto/farstream,kakaroto/farstream,shadeslayer/farstream,pexip/farstream,shadeslayer/farstream,kakaroto/farstream,tieto/farstream,pexip/farstream,tieto/farstream,tieto/farstream,shadeslayer/farstream,shadeslayer/farstream,tieto/farstream,pexip/farstream,tieto/farstream