Minimum solder mask sliver
All you need to do is change the soldermask expansion around the pads. You can open up the footprint in the library editor, select the pads, and in the Inspector change the expansion. Generally an expansion of 0.002 inches (0.051 millimeters) is sufficient, but if you have space you could increase that a bit. The required distance between soldermask openings will depend on your board supplier and their requirements.