The ornamental design for a connector, as shown and described.
FIG. 1 is a first perspective view of a connector showing my new design;
FIG. 2 is a second perspective view thereof;
FIG. 3 is a first side elevational view thereof;
FIG. 4 is a second side elevational view thereof;
FIG. 5 is a third side elevational view thereof;
FIG. 6 is a fourth side elevational view thereof;
FIG. 7 is a top plan view thereof; and,
FIG. 8 is a bottom plan view thereof.
The broken lines shown in the drawings are included for the purpose of illustrating elements of the connector for lighting system and form no part of the claimed design.