The ornamental design for a storagebin, as shown and described.
FIG. 1 is a front perspective view of a storage bin showing our new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a right side elevational view thereof, the left side being a mirror image thereof;
FIG. 4 is a rear elevational view thereof; and,
FIG. 5 is a top plan view thereof.
The broken line showing of details in FIGS. 2 and 4 is included for the purpose of showing environmental portions of the storage bin and forms no part of the claimed design.