The ornamental design for a flexible circuitboard, as shown and described.
FIG. 1 is a perspective view of a flexible circuit board, according to another embodiment of the invention;
FIG. 2 is a top view of the flexible circuit board of FIG. 1;
FIG. 3 is a bottom view of the flexible circuit board of FIG. 1;
FIG. 4 is a first end view of the flexible circuit board of FIG. 1;
FIG. 5 is a second end view of the flexible circuit board of FIG. 1;
FIG. 6 is a first side view of the flexible circuit board of FIG. 1; and,
FIG. 7 is a second side view of the flexible circuit board of FIG. 1.
Any components in the appended drawings shown in broken lines are for illustrative purposes only and form no part of the claimed design or a specified embodiment thereof.