Refactor: libcrmcommon: Remove unused includes in patchset.c

There are some others that may not be needed, and still others that are
transitively included. We'll keep those rather than going down a rabbit
hole. The two that we remove here are unused; we're only using libxml2's
tree header in patchset.c.

Signed-off-by: Reid Wahl <nrwahl@protonmail.com>