Cleanup GameState (#9610)

* Cleanup GameState

* Braint

core/src/mindustry/core/GameState.java

@@ -86,11 +86,12 @@ public class GameState{
     }
 
     public boolean isPaused(){
-        return is(State.paused);
+        return state == State.paused;
     }
 
+    /** @return whether there is an unpaused game in progress. */
     public boolean isPlaying(){
-        return (state == State.playing) || (state == State.paused && !isPaused());
+        return state == State.playing;
     }
 
     /** @return whether the current state is *not* the menu. */