color: mark --no-color as deprecated (--color=never has the same effect)

This should've been marked deprecated when --color was first introduced, but
it was something I overlooked.

hgext/color.py

@@ -256,7 +256,7 b' def _setupcmd(ui, cmd, table, func, effe'
     entry = extensions.wrapcommand(table, cmd, nocolor)
     entry[1].extend([
         ('', 'color', 'auto', _("when to colorize (always, auto, or never)")),
-        ('', 'no-color', None, _("don't colorize output")),
+        ('', 'no-color', None, _("don't colorize output (DEPRECATED)")),
     ])
 
     for status in effectsmap: