contrib: mingw64: do not update d3d9 anymore

The extra APIs were only used by Qt 5 (ANGLE), so it is not necessary anymore since we use Qt 6. See 5edcad34 for reference.

This only removes overriding d3d9 with the up-to-date version. It does not remove d3d9 from the MinGW installation.

Depends on !4783 (merged).