The ornamental design for a shower control, as shown and described.
FIG. 1 is a perspective view of a shower control showing our design;
FIG. 2 is a front elevation view;
FIG. 3 is a rear elevation view;
FIG. 4 is a right side elevation view; the left side elevation view being a mirror image; and,
FIG. 5 is a top plan view; the bottom plan view being a mirror image.
The broken-line disclosure in the views represents portions of the shower control in which the claimed design is embodied, but which form no part of the claimed design.