[llvm-remarkutil] filter: Ignore whitespace in test

[tobias-stadler]

On Windows, the YAML files may or may not be in CRLF format, which can
cause diff to fail. Thus, ignore whitespace to make this more robust.

[tstellar]

It looks like this was a user error on my part. I checked the Getting Started Guide and it says to do git clone --config core.autocrlf=false on Windows. I checked and the CI container for Windows does this. I updated the build script to do this also and it fixed the failure.