The ornamental design for a strap, as shown and described.
FIG. 1 is a partial top perspective view of a strap in accordance with the present invention;
FIG. 2 is a partial top plan view of the strap of FIG. 1;
FIG. 3 is a partial right elevational view of the strap of FIG. 1;
FIG. 4 is front elevational view of the strap of FIG. 1;
FIG. 5 is a partial bottom plan view of the strap of FIG. 1;
FIG. 6 is a partial left elevational view of the strap of FIG. 1; and,
FIG. 7 is a rear elevational view of the strap of FIG. 1.
Portions of FIGS. 1-3, 5-6 are shown as partial fragmented views and portions of FIGS. 1, 2 and 5 have shading lines for illustrative purposes only and form no part of the claimed design.