cleanup: drop unused import from pywatchman

Caught by PyCharm.

Differential Revision: https://phab.mercurial-scm.org/D7735

hgext/fsmonitor/pywatchman/capabilities.py

@@ -29,8 +29,6 b''
 # no unicode literals
 from __future__ import absolute_import, division, print_function
 
-import re
-
 
 def parse_version(vstr):
     res = 0