Remove the DLL dir from the PATH even if it was present while add_dll_directory().
Remove the DLL dir from the PATH even if it was present while add_dll_directory().

This fixes sporadic test failures with RI_FORCE_PATH_FOR_DLL=1.

oneclick/rubyinstaller2,oneclick/rubyinstaller2,larskanis/rubyinstaller2,larskanis/rubyinstaller2,larskanis/rubyinstaller2,oneclick/rubyinstaller2