The ornamental design for a trellis, as shown and described.
FIG. 1 is a top perspective view of a trellis, showing the new design;
FIG. 2 is a bottom perspective view of the trellis illustrated in FIG. 1;
FIG. 3 is a front elevation view of the trellis illustrated in FIG. 1;
FIG. 4 is a back elevation view of the trellis illustrated in FIG. 1;
FIG. 5 is a left side elevation view of the trellis illustrated in FIG. 1;
FIG. 6 is a right side elevation view of the trellis illustrated in FIG. 1;
FIG. 7 is a top plan view of the trellis illustrated in FIG. 1; and,
FIG. 8 is a bottom plan view of the trellis illustrated in FIG. 1.
The dashed broken lines depict portions of the trellis that form no part of the claimed design. The dot-dash broken lines define the bounds of the claim and form no part of the claimed design.