BCP 14 is not needed

[thomas-fossati]

Murray's ballot:

I suggest dropping your use of BCP 14, for two reasons:

(a) You only use one MUST, which could be shed without loss of force by
changing "MUST use" to "uses";

(b) I think the use of MUST in the media type templates is not appropriate
because, when those are copied verbatim to the registry, the BCP 14 template
isn't going to be there to explain what "MUST" (in all caps) means.