The ornamental design for door dolly, as shown and described.
FIG. 1 is a perspective view of a door dolly of the present invention;
FIG. 2 is a front elevational view of the invention;
FIG. 3 is a rear elevational view of the invention;
FIG. 4 is a right-side elevational view of the invention;
FIG. 5 is a left-side elevational view of the invention;
FIG. 6 is a top plan view of the invention;
FIG. 7 is a bottom plan view of the invention; and,
FIG. 8 is a perspective view of the door dolly of the present invention in use, illustrating a door and a rolling surface in phantom outline, the broken lines showing the door and rolling surface for illustrative purposes only and forming no part of the claimed design.