Exclude Markdown files from format-dev runs (#27052)

Summary
--

This should fix the CI failures I was seeing in #27035:


https://github.com/astral-sh/ruff/actions/runs/29854835643/job/88716871906?pr=27035

I guess this didn't appear in #27018 because no formatter files were
modified.

Test Plan
--

CI on this PR, success:
https://github.com/astral-sh/ruff/actions/runs/29861350490/job/88738651835?pr=27052

Author: ntBre

crates/ruff_dev/src/format_dev.rs

@@ -40,7 +40,8 @@ fn parse_cli(dirs: &[PathBuf]) -> anyhow::Result<(FormatArguments, ConfigArgumen
     let args_matches = FormatCommand::command()
         .no_binary_name(true)
         .get_matches_from(dirs);
-    let arguments: FormatCommand = FormatCommand::from_arg_matches(&args_matches)?;
+    let mut arguments: FormatCommand = FormatCommand::from_arg_matches(&args_matches)?;
+    arguments.extend_exclude = Some(vec![FilePattern::Builtin("*.md")]);
     let (cli, config_arguments) = arguments.partition(GlobalConfigArgs::default())?;
     Ok((cli, config_arguments))
 }