In Pragma, "When sending a no-cache request, a client ought to include both the pragma and cache-control directives"
In Pragma, "When the Cache-Control header field is not present in a request, caches must consider the no-cache request pragma-directive as having the same effect as if "Cache-Control: no-cache" were present"
Change Pragmas registration status to "obsoleted"
Remove requirements relating to it.
Retain text explaining its semantics, and note that it's superseded by Cache-Control: no-cache.