Downlight luminaire

FIG. 1 is a front perspective view of the ornamental design for the downlight luminaire;

FIG. 2 is a front view thereof;

FIG. 3 is a right side elevational view thereof;

FIG. 4 is a first side elevational view seen rotated 45 degrees from the view of FIG. 3 ;

FIG. 5 is a second side elevational view seen rotated 45 degrees from the view of FIG. 4 ;

FIG. 6 is a rear view thereof; and,

FIG. 7 is a rear perspective view thereof.

The broken line disclosure is for environmental purposes only, and does not form a part of the claimed design.