[clang] [NFC] Delete unused clang-formatted-files.txt file (PR #109220)

[Rahul Joshi via cfe-commits]

jurahul wrote:

May be. Even in that PR, the only reference to this file is:

```
CLEAN_FILE = os.path.join(CLANG_DIR, 'docs/tools/clang-formatted-files.txt')
cleanfiles = open(CLEAN_FILE, "wb")
```
So its overwritten. But yeah, let @mydeveloperday confirm.



https://github.com/llvm/llvm-project/pull/109220