Plugins: expose rxjs matching 6.4.0 (#17148)

* expose rxjs

* remove super old observable export

public/app/features/plugins/plugin_loader.ts

@@ -75,6 +75,10 @@ exposeToPlugin('angular', angular);
 exposeToPlugin('d3', d3);
 exposeToPlugin('rxjs/Subject', Subject);
 exposeToPlugin('rxjs/Observable', Observable);
+exposeToPlugin('rxjs', {
+  Subject: Subject,
+  Observable: Observable,
+});
 
 // Experimental modules
 exposeToPlugin('prismjs', prismjs);
@@ -84,12 +88,6 @@ exposeToPlugin('slate-plain-serializer', slatePlain);
 exposeToPlugin('react', react);
 exposeToPlugin('react-dom', reactDom);
 
-// backward compatible path
-exposeToPlugin('vendor/npm/rxjs/Rx', {
-  Subject: Subject,
-  Observable: Observable,
-});
-
 exposeToPlugin('app/features/dashboard/impression_store', {
   impressions: impressionSrv,
   __esModule: true,