The ornamental design for a socket, as shown and described.
FIG. 1 is a front view of the socket, showing my new design.
FIG. 2 is a back view thereof.
FIG. 3 is a top view thereof.
FIG. 4 is a bottom view thereof.
FIG. 5 is a left side elevational view thereof.
FIG. 6 is a right side elevational view thereof.
FIG. 7 is a front perspective view thereof; and,
FIG. 8 is a back perspective view thereof.
The masked areas adjacent to the dash-dot broken lines in the drawings depict portions of the socket that form no part of the claimed design. The dash-dot broken lines define the bounds of the claimed design and form no part thereof.