The ornamental design for the luminaire, as shown and described.
FIG. 1 is a bottom front isometric view of our new luminaire design;
FIG. 2 is a top front isometric view thereof;
FIG. 3 is a bottom plan view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a front elevation view thereof;
FIG. 6 is a rear elevation view thereof;
FIG. 7 is a left side elevation view thereof; and,
FIG. 8 is a right side elevation view thereof.
The broken dash lines shown in the drawing views represent non-claimed subject matter, and neither the lines themselves nor anything within the lines form any part of the claimed invention.