fix (core) Remove not need operator || (#11425)

Since the mysterous why things evade in shallow water root issue was finally determined because of our shallow water calculations was wrong that was corrected by pr https://github.com/azerothcore/azerothcore-wotlk/pull/11419 we can now remove this operator

src/server/game/Entities/Creature/Creature.cpp

@@ -3035,7 +3035,7 @@ bool Creature::SetSwim(bool enable)
  */
 bool Creature::CanSwim() const
 {
-    if (Unit::CanSwim() || (!Unit::CanSwim() && !CanFly()))
+    if (Unit::CanSwim())
         return true;
 
     if (IsPet())