The ornamental design for a shower caddy, as shown and described.
FIG. 1 is a perspective view of a shower caddy showing my new design;
FIG. 2 is a first side view thereof, the opposite side being a mirror image of the side shown;
FIG. 3 is a top plan view thereof;
FIG. 4 is a front view thereof;
FIG. 5 is a bottom view thereof; and,
FIG. 6 is a rear perspective view thereof.
The broken line showing in the figures is included for the purpose of illustrating portions of the shower caddy and form no part of the claimed design.