The ornamental design for a footwear upper, as shown and described.
FIG. 1 is a perspective view of a footwear upper in accordance with a fourth embodiment of our design;
FIG. 2 is a front elevational view of the footwear upper in accordance with the fourth embodiment;
FIG. 3 is a back elevational view of the footwear upper in accordance with the fourth embodiment;
FIG. 4 is a left side view of the footwear upper in accordance with the fourth embodiment;
FIG. 5 is a right side view of the footwear upper in accordance with the fourth embodiment; and,
FIG. 6 is a top view of the footwear upper in accordance with the fourth embodiment.
Broken lines are environmental only and form no part of the claimed design. Broken lines adjacent shaded areas of the design represent the bounds of the claimed design and are not themselves a part of the claimed design.