'tramp-cleanup-bufferless-connections' cleans up connection-related objects for which no associated buffers exist.  This is helpful to prune connections after you close remote-file buffers without having to either cherry pick via 'tramp-cleanup-connection' or clear them all via 'tramp-cleanup-all-connections'.

I looked for an equivalent but didn't see one so I've been using this command, and I think it's ready for contribution.

-Stephane