docs: `Lint` -> `Format` in formatter.md (#10777)

## Summary

Since #10217 the [formatter
docs](https://docs.astral.sh/ruff/formatter/) contained

```
ruff format                   # Format all files in the current directory.
ruff format path/to/code/     # Lint all files in `path/to/code` (and any subdirectories).
ruff format path/to/file.py   # Format a single file.
```

I believe the `Lint` here is a copy-paste typo from the [linter
docs](https://docs.astral.sh/ruff/linter/).

## Test Plan

N/A

docs/formatter.md

@@ -12,7 +12,7 @@ directories, and formats all discovered Python files:
 
 ```shell
 ruff format                   # Format all files in the current directory.
-ruff format path/to/code/     # Lint all files in `path/to/code` (and any subdirectories).
+ruff format path/to/code/     # Format all files in `path/to/code` (and any subdirectories).
 ruff format path/to/file.py   # Format a single file.
 ```