call moveObject() after applying waterwalking

This unbreak abot's boat mods: they're continually teleporting
the boats (who is an actor with waterwalking effect). As such, the
physics simulation was never run and the boat never went to sea level.

apps/openmw/mwphysics/physicssystem.cpp

@@ -935,7 +935,7 @@ namespace MWPhysics
         if (mMoveToWaterSurface)
         {
             mPosition.z() = mWaterlevel;
-            mActorRaw->setPosition(mPosition);
+            MWBase::Environment::get().getWorld()->moveObject(mActorRaw->getPtr(), mPosition.x(), mPosition.y(), mPosition.z());
         }
         mOldHeight = mPosition.z();
         mRefpos = mActorRaw->getPtr().getRefData().getPosition();