The ornamental design for a can opener, as shown and described.
FIG. 1 is an upper perspective view of a can opener, showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a top view thereof;
FIG. 5 is a top view thereof;
FIG. 6 is a bottom view thereof;
FIG. 7 is a top view thereof;
FIG. 8 is a top view thereof; and,
FIG. 9 is a top view thereof.
The dot-dot broken lines in FIGS. 1 and 3 to 9 that define the bounds of the claimed design form no part thereof. The dash-dash broken lines in FIGS. 1 to 9 are included for the purpose of illustrating portions of the article that form no part of the claimed design.