The ornamental design for oven mitt, as shown and described.
FIG. 1 is a top perspective view of an oven mitt showing my new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a bottom plan view thereof;
FIG. 4 is rear elevation view thereof;
FIG. 5 is a front elevation view thereof;
FIG. 6 is a right side elevation view thereof; the left side being a mirror image; and,
FIG. 7 is a top and side perspective view thereof, showing the oven mitt in an exemplary use.
The broken lines showing a human hand and a cooking pot in FIG. 7 illustrate environmental subject matter and form no part of the claimed design. The remaining broken-line subject matter illustrates unclaimed features of the article to which the design is applied.