The ornamental design for the fan blade, as shown and described.
FIG. 1 illustrates a perspective view of a fan blade with a portion of a ceiling fan arm shown in broken lines.
FIG. 2 illustrates a front view thereof, but shown without the portion of the ceiling fan arm.
FIG. 3 illustrates a left side view thereof.
FIG. 4 illustrates a top view thereof.
FIG. 5 illustrates a right side view thereof.
FIG. 6 illustrates a bottom view thereof; and,
FIG. 7 illustrates a rear view thereof.
The broken lines shown in FIG. 1 illustrate environmental structure, and the broken lines in the remaining views illustrate portions of the fan blade. None of the broken lines form part of the claimed design.