fix: clear subscription on shareReplay completion

The subscription needs to be cleared to prevent the implementation holding a reference to the completed source. In Angular, not clearing the reference can lead to components not being garbage collected.

Closes ReactiveX#5034

src/internal/operators/shareReplay.ts

@@ -168,6 +168,7 @@ function shareReplayOperator<T>({
         },
         complete() {
           isComplete = true;
+          subscription = undefined;
           subject.complete();
         },
       });