The ornamental design for packaging container, as shown and described.
FIG. 1 is a perspective view of a packaging container showing our new design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan view thereof;
FIG. 6 is a right side elevation view thereof; and,
FIG. 7 is a left side elevation view thereof.
The broken lines in the drawings showing of the packaging container illustrate the portions of the packaging container that form no part of the claimed design.