Revert #124 and #135 (#139)

This seems to be causing a lot of weirdness, presumably because there's
another missing thing like in #135, but I don't know what it might be and
it feels like it might take a while to find. Backing these changes out
to fix develop while we sort it out.

Fixes https://github.com/element-hq/element-web/issues/28179

src/stores/CallStore.ts

@@ -31,6 +31,7 @@ export class CallStore extends AsyncStoreWithClient<{}> {
     public static get instance(): CallStore {
         if (!this._instance) {
             this._instance = new CallStore();
+            this._instance.start();
         }
         return this._instance;
     }