clang-tools-extra/test/clang-modernize/HeaderReplacements/main.cpp: Tweak sed(1) to let paths with a driveletter quoted in *_expected.yaml.

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@190517 91177308-0d34-0410-b5e6-96231b3b80d8