More missing version tags

Author: akarnokd

Diff for: src/main/java/io/reactivex/rxjava3/core/Maybe.java

@@ -549,6 +549,7 @@ public static <T> Flowable<T> concatDelayError(@NonNull Publisher<@NonNull ? ext
      * @return the new {@code Flowable} with the concatenating behavior
      * @throws NullPointerException if {@code sources} is {@code null}
      * @throws IllegalArgumentException if {@code prefetch} is non-positive
+     * @since 3.0.0
      */
     @BackpressureSupport(BackpressureKind.FULL)
     @CheckReturnValue