The ornamental design for a footwear upper, as shown and described.
FIG. 1 is a top perspective view of an embodiment of a footwear upper showing my new design.
FIG. 2 is a right side elevational view thereof.
FIG. 3 is a left 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 broken lines showing the footwear sole and heel loop features are for the purpose of illustrating environmental structure and form no part of the claimed design.