I claim the ornamental design for a shelf bin, as shown and described.
FIG. 1 is a top perspective view of a shelf bin, showing my new design.
FIG. 2 is a front elevational view of the shelf bin.
FIG. 3 is a rear elevational view of the shelf bin.
FIG. 4 is a left side elevational view of the shelf bin.
FIG. 5 is a right side elevational view of the shelf bin.
FIG. 6 is a top plan view of the shelf bin; and,
FIG. 7 is a bottom plan view of the shelf bin.
The broken lines depict portions of the article that form no part of the claimed design. The shelf bin is shown with a symbolic break in its length. The appearance of any portion of the article between the break lines forms no part of the claimed design.