The ornamental design for footwear upper, as shown and described.
FIG. 1 is a front perspective view of the footwear upper embodying the new design;
FIG. 2 is a rear perspective view thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a front view thereof; and,
FIG. 7 is a rear view thereof.
FIGS. 1-7 show features of an article of footwear in broken lines. These features are shown for environmental purposes and do not form any part of the claimed design. Further, the broken lines immediately adjacent the solid-line portions of the design form the boundary of the design, with the broken lines forming no part of the claimed design.