The ornamental design for a cannula, as shown and described.
FIG. 1 is a first perspective view of a first embodiment of the cannula.
FIG. 2 is a second perspective view of the first embodiment of the cannula.
FIG. 3 is a front view of the first embodiment of the cannula.
FIG. 4 is a rear view of the first embodiment of the cannula.
FIG. 5 is a first side view of the first embodiment of the cannula.
FIG. 6 is a second side view of the first embodiment of the cannula, illustrating a side opposite that shown in FIG. 5.
FIG. 7 is a top view of the first embodiment of the cannula; and,
FIG. 8 is a bottom view of the first embodiment of the cannula.
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.