I claim the ornamental design for a paving block, as shown and described.
FIG. 1 is a perspective view of a paving block showing my new design;
FIG. 2 is a top view of the paving block of FIG. 1;
FIG. 3 is a front view of the paving block of FIG. 1;
FIG. 4 is a right side view of the paving block of FIG. 1;
FIG. 5 is a rear view of the paving block of FIG. 1;
FIG. 6 is a left side view of the paving block of FIG. 1; and,
FIG. 7 is a top view of the paving block of FIG. 1 with its environment shown in broken lines.
The broken line showing of the like blocks in FIG. 7 view represents environmental subject matter. The broken lines form no part of the claimed design.