The ornamental design for a relay, as shown and described.
FIG. 1 is a perspective view of a relay;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken lines depict environmental subject matter only and form no part of the claimed design. The oblique short lines in FIGS. 1 and 6 are intended to illustrate that the surface is translucent.