Absolutely! It's very easy to do this and then you don't need the extra pot. Just leave the lid unlatched and don't allow any pressure to build. Then you process it as usual.
What I like to do is leave the lid slightly ajar. If the lid is locked down you still might build up just a tiny bit of pressure and you don't want any pressure at all. And absolutely leave off the weights.
This is very handy because you only need 1 large pot - use it for both pressure canning and water bath canning.
There's only one slight downside to this, and it's really pretty minor. A water bath has the rack for you to be able to pull the jars up out of the water to hang on the end of the pot. I really appreciate having that rack there.
I like being able to let my jars rest for a few minutes after the processing time, then pull them up out of the water to rest again above the hot water for just a few minutes more. Finally I pulled them out of the canner and put them on my butcher block top to cool. Doing these steps helps with siphoning or loosing liquid in your jars.
The other time I like to use that rack is when I want to keep my jars warm. It's super handy to be able to put the rack up above the hot water and put my empty jars in there to stay warm until I'm ready to fill them.
Of course of other ways to do both of those steps so it's really a pretty minor inconvenience. And if you are cramped on space for storing those big pots or if you just want to keep within a budget and only have one pot to purchase then it's really a great option.