The ornamental design of a mop head, as shown and descried.
FIG. 1 is a top, front isometric view of a mop head showing our new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a bottom plan view thereof;
FIG. 4 is a rear elevation view thereof;
FIG. 5 is a front elevation view thereof;
FIG, 6 is right side elevation view thereof; and,
FIG. 7 is a left side elevation view thereof.
Features of the drawing figures shown in dashed lines are for illustrative purposes only and form no part of the claimed design.