The ornamental design for a filtercover, as shown and described.
FIG. 1 is a perspective view of a filter cover, showing my new design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a right-side elevation view thereof;
FIG. 4 is a rear elevation view thereof;
FIG. 5 is a left-side elevation view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The dash-dot-dash broken lines in the drawings depict the boundary of the claimed invention and it is understood that the claim extends to the boundary that forms no part of the claimed design.