The ornamental design for a tourniquet, as shown and described.
FIG. 1 is a perspective view of a tourniquet in a relaxed configuration;
FIG. 2 is a right side view thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a front view thereof;
FIG. 5 is a back view thereof;
FIG. 6 is a perspective view thereof in a taut configuration; and,
FIG. 7 is a side view thereof.
The broken lines in the drawing views are included for the purpose of illustrating a portion of the tourniquet that forms no part of the claimed design