The ornamental design for a luminaire, as shown and described.
FIG. 1 is a top perspective view of a luminaire showing our new design.
FIG. 2 is side elevational view thereof;
FIG. 3 is a vertical cross-sectional view thereof, taken in the direction of line 3-3 of FIG. 1;
FIG. 4 is a top plan view thereof; and,
FIG. 5 is a bottom plan view thereof.
The broken lines disclosure in the views is understood to represent a portion of the article in which the claimed design is embodied, but which forms no part of the claimed design.