The ornamental design for sectional seating, as shown and described.
FIG. 1 is a front elevational view of the sectional seating comprising my new design;
FIG. 2 is a left side elevational view thereof; and,
FIG. 3 is a top plan view thereof.
The broken lines showing seat cushions and the central portion of the backrest members are for environmental purposes only and form no part of the claimed design. The rear which has not been shown forms no part of the claimed design.