The ornamental design for card case, as shown and described.
FIG. 1 is a front perspective view of a card case showing my new design;
FIG. 2 is a front view of the card case sown in FIG. 1;
FIG. 3 is a rear view of the card case sown in FIG. 1;
FIG. 4 is a right side view of the card case sown in FIG. 1 (with the left side view being a mirror image thereof);
FIG. 5 is a top view of the card case sown in FIG. 1; and,
FIG. 6 is a bottom view of the card case sown in FIG. 1.
The shorter length broken lines representing pocket slits are for the purposes of illustrating environment and form no part of the claimed design. The larger broken lines represent stitching and are part of the claimed design.