[llvm] Revert "[FileCheck] Add a diff output option for FileCheck (#187120)" (PR #192803)

[Shivam Gupta via llvm-commits]

https://github.com/xgupta approved this pull request.

I am fine with the revert, reported issue is fixed but I agree with Claude analysis, there are design issues with should be better resolved before doing the fix. 

https://github.com/llvm/llvm-project/pull/192803