I claim the ornamental design for a stadium seat, as shown and described.
FIG. 1 is a front elevational view of a stadium seat showing my new design;
FIG. 2 is a rear elevational view thereof;
FIG. 3 is a left side elevational view thereof;
FIG. 4 is a right side elevational view thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a bottom plan view thereof; and,
FIG. 7 is a perspective view thereof.
The dash-dash lines shown on the front surface of the backrest represent stitching and form part of the claimed design. The additional broken lines shown in the drawings are for the purpose of illustrating portions of the article and form no part of the claimed design.