The ornamental design for a hair covering, as shown and described.
FIG. 1 is a perspective view of a hair covering;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a back elevation view thereof;
FIG. 4 is a first side elevation view thereof;
FIG. 5 is a second side elevation view thereof; and,
FIG. 6 is a top plan view thereof.
The hair covering discloses a contrast in tone. The short broken lines in FIGS. 1 to 6 illustrating exemplary facial features such as eyes, nose, and ears, are environmental subject matter provided to show how the claimed design may appear when worn, and form no part of the claimed design.