The ornamental design for a printer, as shown and described.
FIG. 1 is a top, front, right-side perspective view of a printer;
FIG. 2 is a top, rear, right-side perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a top view thereof;
FIG. 5 is a right-side view thereof; and,
FIG. 6 is a rear view thereof.
The broken lines depict environmental subject matter only and form no part of the claimed design. The dot-dash lines depict a boundary between claimed and unclaimed subject matter, and form no part of the claimed design. The left-side view and the bottom view depict only environmental subject matter, and thus are not illustrated.