When a reaction is simply being quenched with acid, like this example where you simply need to protonate the enolate, we often just write H3O+. However this doesn't mean we're actually adding in some concentrated HCl or sulfuric, but rather we are adding some slightly acidic water (like a saturated solution of NH4Cl). This way it's acidic enough to quench the enolate, but not so acidic as to carry out further unwanted reactions.
Furthermore, after we quench a reaction we work it up and purify it relatively quickly. It's not like we would let this stir for days with some dilute acid. Instead we quench, extract within a few minutes, and probably run a column on it.