Revert "[Clang] Add a warning on invalid UTF-8 in comments."
This reverts commit
cc309721d20c8e544ae7a10a66735ccf4981a11c because it
breaks the following tests on GreenDragon:
TestDataFormatterObjCCF.py
TestDataFormatterObjCExpr.py
TestDataFormatterObjCKVO.py
TestDataFormatterObjCNSBundle.py
TestDataFormatterObjCNSData.py
TestDataFormatterObjCNSError.py
TestDataFormatterObjCNSNumber.py
TestDataFormatterObjCNSURL.py
TestDataFormatterObjCPlain.py
TestDataFormatterObjNSException.py
https://green.lab.llvm.org/green/view/LLDB/job/lldb-cmake/45288/