[Client] Remove "Not implemented" message when activating other player

Serverside scripts can now make lots of different things happen as the result of such activation, which is why the message was no longer current.

apps/openmw/mwclass/npc.cpp

@@ -1005,7 +1005,7 @@ namespace MWClass
             Don't display a dialogue screen for two players interacting with each other
         */
         if (actor == MWMechanics::getPlayer() && mwmp::PlayerList::isDedicatedPlayer(ptr))
-            return std::shared_ptr<MWWorld::Action>(new MWWorld::FailedAction("Not implemented."));
+            return std::shared_ptr<MWWorld::Action>(new MWWorld::FailedAction(""));
         /*
             End of tes3mp addition
         */