The ornamental design for a stair nosing, as shown.
FIG. 1 is a front perspective view of a stair nosing according to the present application.
FIG. 2 is a front view of the stair nosing of FIG. 1.
FIG. 3 is a rear view of the stair nosing of FIG. 1.
FIG. 4 is an enlarged left view of the stair nosing of FIG. 1, shown in larger scale.
FIG. 5 is an enlarged right view of the stair nosing of FIG. 1, shown in larger scale.
FIG. 6 is a top view of the stair nosing of FIG. 1; and,
FIG. 7 is a bottom view of the stair nosing of FIG. 1.
The stair nosing is shown with one of the ends with a break shown in broken lines. It being understood that the broken lines and anything beyond the break is not part of the claimed design.