The ornamental design for a leg covering, as shown and described.
FIG. 1 is a left side elevational view of a leg covering showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a right side elevational view thereof; and,
FIG. 4 is a rear elevational view thereof.
The specific patterns shown by the stippled surface shading are only representative of the two sections and the two contrasting sections and are not claimed as part of the design, and the sections of the drawing shown in phantom are not claimed as part of the design.