The ornamental design for a decanter, as shown and described.
FIG. 1 is a front, isometric view of a decanter, showing my new design;
FIG. 2 is a front elevational view of FIG. 1;
FIG. 3 is a rear elevational view of FIG. 1;
FIG. 4 is a right-side elevational view of FIG. 1;
FIG. 5 is a left-side elevational view of FIG. 1;
FIG. 6 is a top plan view of FIG. 1;
FIG. 7 is a bottom plan view of FIG. 1; and,
FIG. 8 is an exploded isometric view of FIG. 1.
The broken lines showing the decanter holder illustrate environmental subject matter and form no part of the claimed design. The remaining broken lines show features of the decanter that form no part of the claimed design.