Remove mention of materializer from streams quickstart (akka#29169)

akka-docs/src/main/paradox/stream/stream-quickstart.md

@@ -282,8 +282,8 @@ Scala
 Java
 :   @@snip [TwitterStreamQuickstartDocTest.java](/akka-docs/src/test/java/jdocs/stream/TwitterStreamQuickstartDocTest.java) { #authors-foreach-println }
 
-Materializing and running a stream always requires a `Materializer` to be @scala[in implicit scope (or passed in explicitly,
-like this: `.run(materializer)`)]@java[passed in explicitly, like this: `.run(mat)`].
+Materializing and running a stream always requires an `ActorSystem` to be @scala[in implicit scope (or passed in explicitly,
+like this: `.runWith(sink)(system)`)]@java[passed in explicitly, like this: `.runWith(sink, system)`].
 
 The complete snippet looks like this:
 
@@ -414,8 +414,7 @@ has also a type parameter of @scala[`Future[Int]`]@java[`CompletionStage<Integer
 
 This step does *not* yet materialize the
 processing pipeline, it merely prepares the description of the Flow, which is now connected to a Sink, and therefore can
-be `run()`, as indicated by its type: @scala[`RunnableGraph[Future[Int]]`]@java[`RunnableGraph<CompletionStage<Integer>>`]. Next we call `run()` which uses the @scala[implicit] `Materializer`
-to materialize and run the Flow. The value returned by calling `run()` on a @scala[`RunnableGraph[T]`]@java[`RunnableGraph<T>`] is of type `T`.
+be `run()`, as indicated by its type: @scala[`RunnableGraph[Future[Int]]`]@java[`RunnableGraph<CompletionStage<Integer>>`]. Next we call `run()` which materializes and runs the Flow. The value returned by calling `run()` on a @scala[`RunnableGraph[T]`]@java[`RunnableGraph<T>`] is of type `T`.
 In our case this type is @scala[`Future[Int]`]@java[`CompletionStage<Integer>`] which, when completed, will contain the total length of our `tweets` stream.
 In case of the stream failing, this future would complete with a Failure.