I claim the ornamental design for a toilet tank lid, as shown and described.
FIG. 1 is a perspective view of an embodiment of the claimed design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof; and,
FIG. 6 is a top view thereof.
The ornamental design which is claimed is shown in solid lines in the drawings. The broken lines in the drawings are for illustrative purposes only and form no part of the claimed design. Broken lines formed by equal length dashes in the drawings illustrate unclaimed portions of the design. Broken lines formed of unequal length dashes (i.e., dash-dot) show boundaries between claimed and unclaimed portions of the design.