Remove usr.bin/clang/llvm-ar/llvm-cxxfilt-driver.cpp file

I accidentally copied this to the wrong place, or by accident to two
places, during the merge of llvmorg-17-init-19304-gd0b54bb50e51.

Fixes: 06c3fb2749bd
MFC after: 3 days

(cherry picked from commit 4015c064200e643ab110cdf831064c3c73f31b73)