The ornamental design for an upper for a shoe, as shown and described.
FIG. 1 is a perspective view of an upper for a shoe in accordance with my new design;
FIG. 2 is a top view thereof;
FIG. 3 is a right view thereof;
FIG. 4 is a left view thereof;
FIG. 5 is a front view thereof; and,
FIG. 6 is a rear view thereof.
The dotted lines shown in all of the figures are for environmental purposes and form no part of the claim. The dashed lines with a solid line through them are stitching and form a part of the claim.