I claim the ornamental design for an earring, as shown and described.
FIG. 1 is a front, top, and left side perspective view of an earring, showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan view thereof;
FIG. 6 is a right side elevational view thereof; and,
FIG. 7 is a left side elevational view thereof.
The features shown in broken lines in the drawings form no part of the claimed design. The dot-dashed lines denote the boundary of the claim, and form no part of the claimed design.