Purl 2 stitches together is a common single stitch decrease on the purl side with a right lean. When patterns don't specify a type of decrease on the purl side, they generally mean this stitch or any other you might prefer.

To make this stitch, insert the right hand needle into the working stitch and the next stitch purlwise, wrap yarn around the right hand needle and draw through both stitches, slide both worked stitches off the left hand needle leaving the new stitch on the right hand needle.