Section 5.5.1: RFC 8122 consistency

[aboba]

From EKR: https://lists.w3.org/Archives/Public/public-webrtc/2017May/0166.html

One of the the hash function algorithms defined in the 'Hash function
Textual Names' registry, initially specified in [ RFC4572] Section
8. As noted in [JSEP] Section 5.2.1, the digest algorithm used for the
fingerprint matches that used in the certificate signature.

I see that this was relaxed in RFC 8122. I wonder if we want to relax it here and in JSEP.

[aboba]

My suggestion is to delete the second sentence, since the text has changed in JSEP:

For DTLS, all m= sections MUST use all the certificate(s) that have
been specified for the PeerConnection; as a result, they MUST all
have the same [I-D.ietf-mmusic-4572-update] fingerprint value(s), or
these value(s) MUST be session-level attributes.