Fix documentation for editor vim plugin ALE (#13348)

The documented configuration did not work. On failure, ALE suggest to
run `ALEFixSuggest`, into with it documents the working configuration
key

'ruff_format' - Fix python files with the ruff formatter.

Fix an inaccuracy in the documentation, regarding the ALE plugin for the
Vim text editor.

docs/editors/setup.md

@@ -153,7 +153,7 @@ extension for [coc.nvim](https://github.com/neoclide/coc.nvim).
 " Linter
 let g:ale_linters = { "python": ["ruff"] }
 " Formatter
-let g:ale_fixers = { "python": ["ruff-format"] }
+let g:ale_fixers = { "python": ["ruff_format"] }
 ```
 
 </details>