The ornamental design for a drinkingstraw, as shown and described.
FIG. 1 is a perspective view of the drinking straw embodying the new design;
FIG. 2 is an enlarged left view thereof;
FIG. 3 is an enlarged right view thereof;
FIG. 4 is a top view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is a rear view thereof; and,
FIG. 7 is a front view thereof.
FIGS. 1-7 show the drinking straw includes a symbolic break along its length drawn in broken lines. The broken lines and the area between the break lines form no part of the claimed design.