No. That's the slide release.

There is no external "safety" on the Sig P229. The other lever, in front of the slide lock you have indicated, is the de-cock lever. I suppose some would call it a "safety", but it really isn't. It just de-cocks the pistol without firing it.

This is a double action pistol. To fire the gun, you simply need to pull the trigger, whether it is cocked or not. There is no "safety" on this model handgun that disables this feature.