[Trivial] [logging] Rm extraneous cleansubver in serveral debug messages.

We log the cleanSubVer as part of connect. It is not uniquely more informative
than any of the other data we have about a peer, often less. It's also often
long now as well. There is no need to output it as part of mempoolrej,
AcceptToMemoryPool, or pong entries. Leaving it out makes our log entries
more uniform and consistent.