The ornamental design for a footwear upper, as shown and described.
FIG. 1 is a front perspective view of a footwear upper showing our new design;
FIG. 2 is a side elevational view thereof;
FIG. 3 is an opposite side elevational view thereof;
FIG. 4 is a front elevational view thereof;
FIG. 5 is a rear elevational view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The dot-dot-dash broken lines depict the bounds of the claim. The even dashed broken lines depict features of the footwear upper that form no part of the claimed design. The remaining even dashed broken lines showing the shoe sole form no part of the claimed design.