The ornamental design for a cableholder, as shown and described.
FIG. 1 is a perspective view of a cable holder showing my new design;
FIG. 2 is a front view thereof, the rear view being an identical image;
FIG. 3 is a right side view thereof, the left view being an identical image;
FIG. 4 is a top view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is a perspective view thereof, shown in a state of use with environment; and,
FIG. 7 is another perspective view thereof, shown in a state of use with environment.
The broken lines immediately adjacent to the full line showing of the claimed design represent the bounds of the claimed design while all other broken lines are directed to environment and are for illustrative purposes only; the broken lines form no part of the claimed design.