color: fix grammar in help text

hgext/color.py

@@ -1,31 +1,31 b''
 # color.py color output for Mercurial commands
 #
 # Copyright (C) 2007 Kevin Christen <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 '''enable Mercurial color mode (DEPRECATED)
 
-This extensions enable Mercurial color mode. The feature is now directly
+This extension enables Mercurial color mode. The feature is now directly
 available in Mercurial core. You can access it using::
 
   [ui]
   color = auto
 
 See :hg:`help color` for details.
 '''
 
 from __future__ import absolute_import
 
 from mercurial import color
 
 # Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for
 # extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
 # be specifying the version(s) of Mercurial they are tested with, or
 # leave the attribute unspecified.
 testedwith = 'ships-with-hg-core'
 
 def extsetup(ui):
     # change default color config
     color._enabledbydefault = True