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 environment for the lamp;
FIG. 2 is a front elevation view of the lamp housing in accordance with my design;
FIG. 3 is a top view of the lamp housing in accordance with my design; and,
FIG. 4 is a bottom plan view of the lamp housing in accordance with my design.
The right and left elevation views are symmetrical and the front and rear elevation views are symmetrical. The broken lines showing environmental structure are for illustrative purposes only and form no part of the claimed design.