Fix misleading config in app template

Uncommenting the sys.config shell setting in app template rebar.config
works now as expected.

priv/templates/app_rebar.config

@@ -2,6 +2,6 @@
 {deps, []}.
 
 {shell, [
-  % {config, [{config, "config/sys.config"}]},
+  % {config, "config/sys.config"},
     {apps, [{{name}}]}
 ]}.