The ornamental design for a golfballcupinsert, as shown and described.
FIG. 1 is a top-front-left perspective view of a golf ball cup insert showing my new design;
FIG. 2 is a bottom-rear-right perspective view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a rear elevational view thereof;
FIG. 5 is a left-side elevational view thereof;
FIG. 6 is a right-side elevational view thereof;
FIG. 7 is a top plan view thereof;
FIG. 8 is a bottom plan view thereof; and,
FIG. 9 is a cross-sectional view taken along line 9-9 in FIG. 7.
The broken lines showing a plurality of drainage holes in FIG. 1 through 9 and the fixture holes in FIGS. 1, 5, 6, and 9 show portions of the golf ball cup insert that forms no part of the claimed design.