The ornamental design for a bridlebit for a horse, as shown and described.
FIG. 1 is a perspective view of the bridle bit of the invention showing the overall profile of the bridle bit, the horse being shown in unclaimed broken lines to help explain the general environment of the invention;
FIG. 2 is a front view of the bridle bit of FIG. 1;
FIG. 3 is a right side view of the bridle bit, the left side view forming a mirror image thereof;
FIG. 4 is a rear view of the bridle bit of the invention;
FIG. 5 is a top plan view of the bridle bit of FIG. 1; and,