The ornamental design for a ledlantern, as shown and described.
FIG. 1 is a front elevational view of a LED lantern showing my new design;
FIG. 2 is a rear elevational view thereof;
FIG. 3 is a left side elevational view thereof;
FIG. 4 is a right side elevational view thereof;
FIG. 5 is a top plan view thereof; and,
FIG. 6 is a bottom view thereof.
The broken line showing of lantern-supporting structure in FIGS. 1-5 and a battery compartment cover in FIG. 6 is for illustrative purposes only and forms no part of the claimed design.