removing some old portal mode code that's unused

while auditing Tower strings

awx/ui/client/lib/services/app.strings.js

@@ -0,0 +1,9 @@
+// The purpose of this file is to instantiate the BaseStringService
+// for app-wide usage. 
+function AppStrings (BaseString) {
+    BaseString.call(this, 'app');
+}
+
+AppStrings.$inject = ['BaseStringService'];
+
+export default AppStrings;