templatekw: remove unneeded showtags

Now that we have the machinery of namespaces in-place, we use that instead of
hand-rolling our own template function.

Note, this can only be used for tags because both branches and bookmarks have
special case logic for 'default' and the current bookmark (which is something
outside the namespace api for now).

mercurial/templatekw.py

@@ -374,10 +374,6 b' def showsubrepos(**args):'
             subrepos.append(sub) # removed in ctx
     return showlist('subrepo', sorted(subrepos), **args)
 
-def showtags(**args):
-    """:tags: List of strings. Any tags associated with the changeset."""
-    return showlist('tag', args['ctx'].tags(), **args)
-
 def shownames(namespace, **args):
     """helper method to generate a template keyword for a namespace"""
     ctx = args['ctx']
@@ -424,7 +420,6 b' keywords = {'
     'phaseidx': showphaseidx,
     'rev': showrev,
     'subrepos': showsubrepos,
-    'tags': showtags,
 }
 
 def _showparents(**args):