I claim the ornamental design for a planter, as shown and described.
FIG. 1 is a front view of a planter of a first embodiment showing the design.
FIG. 2 is a front view of a planter of a second embodiment showing the design; and,
FIG. 3 is a front view of a planter of a third embodiment showing the design.
The portions of the planter not shown and the portions shown in dotted lines are not part of the claimed design. The broken lines showing the planters are for illustrative purposes only and form no part of the claimed design.