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.

hgext/sparse.py

@@ -68,14 +68,6 b' def extsetup(ui):'
         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'):