I claim the ornamental design for a syringe, as shown and described.
FIG. 1 is a bottom left perspective view of the syringe;
FIG. 2 is top left perspective view of the syringe;
FIG. 3 is a front elevational view of the syringe, the rear elevation view being the same as the front elevation view;
FIG. 4 is a right side elevational view of the syringe, the left side elvation view being the same as the right elevation view;
FIG. 5 s a top plan view of the syringe; and,
FIG. 6 is a bottom plan view of the syringe.
The broken line showing of parts of the drawings is included for the purpose of illustrating use and environment and forms no part of the claimed design.