chore(Observable): deprecate create method (#3982)

src/internal/Observable.ts

@@ -49,6 +49,7 @@ export class Observable<T> implements Subscribable<T> {
    * @param {Function} subscribe? the subscriber function to be passed to the Observable constructor
    * @return {Observable} a new cold observable
    * @nocollapse
+   * @deprecated use new Observable() instead
    */
   static create: Function = <T>(subscribe?: (subscriber: Subscriber<T>) => TeardownLogic) => {
     return new Observable<T>(subscribe);

src/internal/Subject.ts

@@ -39,7 +39,9 @@ export class Subject<T> extends Observable<T> implements SubscriptionLike {
     super();
   }
 
-  /**@nocollapse */
+  /**@nocollapse
+   * @deprecated use new Subject() instead
+  */
   static create: Function = <T>(destination: Observer<T>, source: Observable<T>): AnonymousSubject<T> => {
     return new AnonymousSubject<T>(destination, source);
   }