I claim the ornamental design for a wrench, as shown and described.
FIG. 1 is a perspective view of a wrench showing my new design;
FIG. 2 is another perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a back view thereof;
FIG. 5 is a left view thereof;
FIG. 6 is a right view thereof;
FIG. 7 is a top view thereof; and,
FIG. 8 is a bottom view thereof.
The broken lines form no part of the claimed design, and any shading is provided to illustrate contour only and is not an indication of texture, gloss, etc.