The ornamental design for a shower armset, as shown and described.
FIG. 1 is a front and top perspective view of a shower arm set, showing my new design;
FIG. 2 is a rear and bottom perspective view thereof;
FIG. 3 is a front elevation view thereof;
FIG. 4 is a rear elevation view thereof;
FIG. 5 is a left side elevation view thereof;
FIG. 6 is a right side elevation view thereof;
FIG. 7 is a top plan view thereof;
FIG. 8 is a bottom plan view thereof; and,
FIG. 9 is an enlarged view of a portion indicated with numeric 9 in FIG. 2.
The broken lines in the figures illustrate portions of the shower arm set that form no part of the claimed design. The dash dot dash lines in FIGS. 2 and 9 are for the purpose of depicting the boundary lines of the enlarged view and form no part of the claimed design.