Set ed.keydelay to 6 when returning to editor

This fixes an annoying bug where if you use Up or Down to press ACTION
on the "All crewmates rescued!" dialogue whenever you rescue the last
crewmate during playtesting, it'll move you to the room above or below
you. This is because ed.keydelay isn't set to 6 (which is the standard
value that it gets set to whenever you press most keys in the editor),
but now it is.

desktop_version/src/Game.cpp

@@ -7306,6 +7306,8 @@ void Game::returntoeditor()
     graphics.showcutscenebars = false;
     graphics.fademode = 0;
 
+    ed.keydelay = 6;
+
     graphics.backgrounddrawn=false;
     music.fadeout();
     //If warpdir() is used during playtesting, we need to set it back after!