Is it safe to put a window a/c unit over kitchen sink window?
The inside workings of a window A/C are typically wet. The coils get tons of condensation, the fan in the back splashes the condensate water all over, it's fine there. If anything it is safer since it is being plugged into a GFCI protected receptacle where typically they are not.

Just be careful of the load and whatever else is plugged into the same circuit. You may need to turn off the A/C to use some appliances.