[OptDiag] Remove non-printable chars from function name

The r283656 did this in the remark arguments.  We also need to do this
in the main function attribute as that is written to YAML as well.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@286482 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed