The ornamental design for a cardholder, as shown and described.
FIG. 1 is an isometric front view of the present invention in an open configuration.
FIG. 2 is a rear view of the present invention in an open configuration.
FIG. 3 is rear view of the present invention in a closed configuration.
FIG. 4 is a right side view of the present invention in a closed configuration.
FIG. 5 is a left side view of the present invention in a closed configuration.
FIG. 6 is a top view of the present invention in a closed configuration; and,
FIG. 7 is a bottom view of the present invention in a closed configuration.
The broken lines of even length in the drawings illustrate stitching and form part of the claimed design. The broken lines of uneven length in drawing FIGS. 1 and 2, including all text shown, illustrate environmental subject matter that forms no part of the claimed design.