The ornamental design for a lockingshelf, as shown and described.
FIG. 1 is a front perspective view of the locking shelf;
FIG. 2 is a left side elevational view of the locking shelf of FIG. 1;
FIG. 3 is a right side elevational view of the locking shelf of FIG. 1;
FIG. 4 is a top plan view of the locking shelf of FIG. 1;
FIG. 5 is a bottom plan view of the locking shelf of FIG. 1;
FIG. 6 is a front elevational view of the locking shelf of FIG. 1; and,
FIG. 7 is a rear elevational view of the locking shelf of FIG. 1.
The broken lines shown in the drawings form no part of the claimed design. The separations and brackets indicate that the precise height and width of the design is not claimed.