The ornamental design for a sconce, as shown and described.
FIG. 1 is a perspective view of a first embodiment of a sconce showing my new design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a right side elevation view thereof, the left side being a mirror image;
FIG. 4 is a top plan view thereof, the bottom being a mirror image;
FIG. 5 is a perspective view of a second embodiment of a sconce showing my new design;
FIG. 6 is a front elevation view thereof;
FIG. 7 is a right side elevation view thereof, the left side being a mirror image; and,
FIG. 8 is a top plan view thereof, the bottom being a mirror image.
The second embodiment is shown with symbolic breaks in height in FIGS. 5-7, and those portions of the article between the break lines form no part of the claimed design.