We claim the ornamental design for a pipette, as shown and described.
FIG. 1 is a perspective view of the pipette, showing a new design;
FIG. 2 is a front view thereof;
FIG. 3 is a right side view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a top view thereof; and,
FIG. 6 is a bottom view thereof.
The broken lines in the drawings are included for the purpose of illustrating portions of the pipette that form no part of the claimed design.