The ornamental design for a filterhousing, as shown and described.
FIG. 1 is a perspective view, showing the new design for a filter housing;
FIG. 2 is a front view thereof;
FIG. 3 is a right side view thereof, the left side being a mirror image thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a top view thereof; and,
FIG. 6 is a bottom view thereof.
The phantom line showing forms no part of the claimed design, and the surface shading lines are provided to illustrate contour only; they are not an indication of texture, gloss, etc.