The ornamental design for a sling mount, as shown and described.
FIG. 1 is a perspective view of the sling mount;
FIG. 2 is another perspective view thereof;
FIG. 3 is a perspective view of a first portion of the sling mount;
FIG. 4 is a top view of the first portion thereof;
FIG. 5 is a bottom view of the first portion thereof;
FIG. 6 is a left side view of the first portion thereof;
FIG. 7 is a right side view of the first portion thereof;
FIG. 8 is a back view of the first portion thereof; and,
FIG. 9 is a front view of the first portion thereof.
The broken lines immediately adjacent the shaded areas represent the bounds of the claimed design while all other broken lines are directed to environment and are for illustrative purposes only; the broken lines form no part of the claimed design.