Fix singular wording

Author: akarnokd

src/main/java/io/reactivex/rxjava3/core/Flowable.java

@@ -19236,7 +19236,7 @@ public final <U, V> Flowable<Flowable<T>> window(
      *
      * <p>Note that this operator doesn't emit anything until the other source has produced at
      * least one value. The resulting emission only happens when the current {@code Flowable} emits (and
-     * not when any of the other sources emit, unlike combineLatest).
+     * not when the other source emits, unlike combineLatest).
      * If the other source doesn't produce any value and just completes, the sequence is completed immediately.
      * If the upstream completes before the other source has produced at least one value, the sequence completes
      * without emission.

src/main/java/io/reactivex/rxjava3/core/Observable.java

@@ -16077,7 +16077,7 @@ public final <U, V> Observable<Observable<T>> window(
      *
      * <p>Note that this operator doesn't emit anything until the other source has produced at
      * least one value. The resulting emission only happens when the current {@code Observable} emits (and
-     * not when any of the other sources emit, unlike combineLatest).
+     * not when the other source emits, unlike combineLatest).
      * If the other source doesn't produce any value and just completes, the sequence is completed immediately.
      * If the upstream completes before the other source has produced at least one value, the sequence completes
      * without emission.