The ornamental design for a beaniecap, as shown and described.
FIG. 1 is a left side view of a first embodiment of a beanie cap;
FIG. 2 is a left side view of a second embodiment thereof;
FIG. 3 is a left side view of a third embodiment thereof; and,
FIG. 4 is a left side view of a fourth embodiment thereof.
The broken lines represent boundaries of the claimed design, and form no part of the claimed design. The white rectangular shapes surrounded by broken line boundaries depict portions of the beanie cap that form no part of the claimed design.