FIX: Renaming and deleting tags (#11169)

The REST adapter generates paths with the /tags/ prefix indescriminately,
but individual tag paths have been moved under the /tag/ prefix to allow
tags with names that would otherwise cause ambiguity like c.

app/assets/javascripts/discourse/app/adapters/tag.js

@@ -0,0 +1,7 @@
+import RESTAdapter from "discourse/adapters/rest";
+
+export default RESTAdapter.extend({
+  pathFor(store, type, id) {
+    return id ? `/tag/${id}` : `/tags`;
+  },
+});