Fix description of the format.skip-magic-trailing-comma example (#19095)

## Summary

This PR fixes a typo in the docs, where both variants of a config have
the same description.

crates/ruff_workspace/src/options.rs

@@ -3587,7 +3587,7 @@ pub struct FormatOptions {
     /// Setting `skip-magic-trailing-comma = true` changes the formatting to:
     ///
     /// ```python
-    /// # The arguments remain on separate lines because of the trailing comma after `b`
+    /// # The arguments are collapsed to a single line because the trailing comma is ignored
     /// def test(a, b):
     ///     pass
     /// ```