ruff

6bc1ba6d - Use stdin for formatter when `--stdin-filename` is provided (#6926)

Use stdin for formatter when `--stdin-filename` is provided (#6926) ## Summary Just making the formatter CLI more consistent with the linter -- e.g., we now use stdin on invocations like `cat foo.py | cargo run -p ruff_cli -- format -- --stdin-filename=foo.py`, instead of _only_ relying on the `-` file (and use the same helper as the linter to facilitate this).