Remove words such as simply and obviously from docs (#25095)

* One does not "simply"

* It's not obvious

* It's not really _that_ easily done

* Basically is basically a useless word

* Of course - if you already know how things work you wouldn't be reading the docs

* Clearly is maybe not so clear for everyone

* Just was just a bit harder as there are some uses that are just

akka-docs/src/test/java/jdocs/stream/GraphStageDocTest.java

@@ -594,7 +594,7 @@ public class GraphStageDocTest extends AbstractJavaTest {
               promise.complete(elem);
               push(out, elem);
 
-              // replace handler with one just forwarding
+              // replace handler with one that only forwards elements
               setHandler(in, new AbstractInHandler() {
                 @Override
                 public void onPush() {