Remove `ActionView::Renderer#render_template`

This seems to be making a pair with `#render_partial` but in reality
it's no longer refered to from anywhere. Since it is marked with
nodoc, I propose to get rid of it.

As far as I can tell from my non-comprehensive research,
this method was introduced in the commit b735761,
became practically private in f984907 and unused in 1bc0a59.

actionview/lib/action_view/renderer/renderer.rb

@@ -45,12 +45,6 @@ module ActionView
       end
     end
 
-    # Direct access to template rendering.
-    def render_template(context, options) # :nodoc:
-      render_template_to_object(context, options).body
-    end
-
-    # Direct access to partial rendering.
     def render_partial(context, options, &block) # :nodoc:
       render_partial_to_object(context, options, &block).body
     end