go-sdl2: Workaround for static libraries breaks `go get -u`

After 9515279986a1fc8d043e301522c565a0b8b56480 it’s no longer possible to update all dependencies in a project that use go-sdl2.

Normally this would be done by running go get -u ./..., but after the dummy package was added the go command fails:

go: malformed module path "github.com/veandco/go-sdl2/.go-sdl2-libs": leading dot in path element
go: malformed module path "github.com/veandco/go-sdl2/.go-sdl2-libs/include/SDL2": leading dot in path element

Go version: 1.20.2 Go-SDL2 version: 0.4.33 OS: macos Architecture: arm64