The ornamental design for an inflatablejersey, as shown and described.
FIG. 1 is a top, front, and right perspective view of an inflatable jersey showing my new design, the phantom showing of a team logo not being part of the claimed design;
FIG. 2 is an upper, back, and right perspective view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a back elevation view thereof;
FIG. 5 is a left side elevational view thereof;
FIG. 6 is a right side elevation view thereof;
FIG. 7 is a top plan view thereof; and,
FIG. 8 is a bottom plan view thereof.
Surface indicia, including a phantom display of a team logo, for example, that may be shown in the drawing figures is disclaimed as not being a part of the claimed ornamental design.