sparse: remove reference to hgwatchman

sparse: remove reference to hgwatchman

This is a legacy extension. Now that the extension is in core,
we only need to support what's in core, which is fsmonitor.

--- a/hgext/sparse.py	Sat Jul 01 10:36:03 2017 -0700
+++ b/hgext/sparse.py	Sat Jul 01 10:24:31 2017 -0700
@@ -68,14 +68,6 @@
         extensions.wrapfunction(fsmonitor, '_hashignore', _hashignore)
     except KeyError:
         pass
-    # do the same for hgwatchman, old name
-    try:
-        hgwatchman = extensions.find('hgwatchman')
-        def _hashignore(orig, ignore):
-            return _hashmatcher(ignore)
-        extensions.wrapfunction(hgwatchman, '_hashignore', _hashignore)
-    except KeyError:
-        pass
 
 def reposetup(ui, repo):
     if not util.safehasattr(repo, 'dirstate'):