The ornamental design for a side fairing, as shown and described.
FIG. 1 is a front perspective view of a side fairing showing my new design,
it being understood that the broken lines are for illustrative purposes
only and form no part of the design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is an outer side elevation view thereof; and