The ornamental design or a tub spout, as shown and described.
FIG. 1 is a perspective view of a tub spout showing my new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a bottom view thereof;
FIG. 4 is a left side view thereof, the opposite side being a mirror image of the side shown;
FIG. 5 is a front end view thereof; and,
FIG. 6 is a rear view thereof.
The broken line showing a portion of the faucet is included for the purpose of illustrating a portion of the faucet that forms no part of the claimed design.