The ornamental design for a cabinet vent cover, as shown and described.
FIG. 1 is a perspective view of a cabinet vent cover in use condition.
FIG. 2 is a front elevational view of the cabinet vent cover.
FIG. 3 is a top plan view thereof.
FIG. 4 is a bottom plan view thereof.
FIG. 5 is a right side elevational view thereof.
FIG. 6 is a left side elevational view thereof; and,
FIG. 7 is a rear elevational view thereof.
The broken line showings of portions of the rear of the cabinet vent cover form no part of the claimed design. The broken line showing of a cabinet door illustrates the environment of the claimed design and forms no part thereof.