The ornamental design for a toilettrainingdevice, as shown and described.
FIG. 1 is an illustration of a perspective view of the toilet training device showing my new design.
FIG. 2 is an illustration of rear view thereof.
FIG. 3 is an illustration of a side view thereof.
FIG. 4 is an illustration of a front view thereof.
FIG. 5 is an illustration of a top view thereof; and,
FIG. 6 is an illustration of a bottom view thereof.
The broken lines showing the suction cups, the basketball hoop, and the adjustment holes are for the purpose of illustrating environmental structure and unclaimed subject matter, and form no part of the claimed design.