The ornamental design for a shower diverter trim, as shown and described.
FIG. 1 is a perspective view of a shower diverter trim showing our design;
FIG. 2 is a front elevational view;
FIG. 3 is a rear elevational view;
FIG. 4 is a side elevational view;
FIG. 5 is a side elevational view;
FIG. 6 is a top plan view; and,
FIG. 7 is a bottom plan view.
The broken line disclosures in the view represents portions of the shower diverter trim in which the claimed design is embodied, but which forms no part of the claimed design.