[clang-tools-extra] [tool] Remove legacy argument `-ignore-insert-conflict` from `run-clang-tidy.py` (PR #127066)

[Piotr Zegar via cfe-commits]

https://github.com/PiotrZSL commented:

Best would be to add that option to script and let user decide whatever use it or not.

https://github.com/llvm/llvm-project/pull/127066