The ornamental design for a retainingshoe, as shown and described.
FIG. 1 is a perspective view a retaining shoe according to our new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a bottom plan view thereto;
FIG. 4 is a front elevation view thereof;
FIG. 5 is a rear elevation view thereof;
FIG. 6 is a right side elevation view thereof; and,
FIG. 7 is a left side elevation view thereof.
The broken lines immediately adjacent shaded areas are included for the purpose of representing boundaries and environment. All other broken lines are included for the purpose of illustrating environment and form no part of the claimed design.