[clang-format] Remove (SourceManager, FileID) variants

In Format, remove the reformat() and clean() functions taking a SourceManager
and a FileID. Keep the versions taking StringRef Code.

- there was duplicated functionality
- the FileID versions were harder to use
- the clean() version is dead code anyways

Patch by Krasimir Georgiev. Thank you.

llvm-svn: 286243