The ornamental design for an upper heatgrill, as shown and described.
FIG. 1 is a top view of a upper heat grill showing my new design;
FIG. 2 is a left side view thereof;
FIG. 3 is a front view thereof; and,
FIG. 4 is perspective view thereof.
The broken lines in the drawings are included for the purpose of illustrating portions of the upper heat grill that form no part of the claimed design.