The ornamental design for the lamp housing, as shown and described.
FIG. 1 is a side elevation view of the lamp housing in accordance with my design, illustrating a possible environmental for the lamp;
FIG. 2 is a top plan view of the lamp housing in accordance with my design; and,
FIG. 3 is a bottom plan view of the lamp housing in accordance with my design.
The right, left, front and rear elevation views are substantially identical. The broken lines showing environmental structure are for illustrative purposes only and form no part of the claimed design.