Delete unused mingw bins am: 5f7f053b5f

Original change: https://android-review.googlesource.com/c/platform/prebuilts/gcc/linux-x86/host/x86_64-w64-mingw32-4.8/+/1886652

Change-Id: I9816e8cdd81153b91391fdeab2c2e2c21da62326