The ornamental design for a case, as shown and described.
FIG. 1 is an isometric view of a case showing our new design.
FIG. 2 is a front view thereof.
FIG. 3 is a top view thereof.
FIG. 4 is a left side view thereof.
FIG. 5 is a right side view thereof.
FIG. 6 is a bottom view thereof; and,
FIG. 7 is a rear view thereof.
The broken line showing of environment in the drawings is included for the purpose of illustrating only and forms no part of the claimed design.