core: what rustfmt actually wanted

Three from the checker's own diff. Two are the rule I had guessed at: when a
call overflows and its last argument is a closure, rustfmt keeps the earlier
arguments on the line and expands the closure into a block, rather than putting
every argument on its own line.

The third is a stray double blank line before the test module.

core/src/local/derive.rs

@@ -396,7 +396,10 @@ mod tests {
         assert_eq!(append_item("a note", "milk", false), "a note\n\n- [ ] milk");
         // Nothing between consecutive items.
         let one = "a note\n\n- [ ] milk";
-        assert_eq!(append_item(one, "eggs", false), format!("{one}\n- [ ] eggs"));
+        assert_eq!(
+            append_item(one, "eggs", false),
+            format!("{one}\n- [ ] eggs")
+        );
         // A list-only note starts at the first line.
         assert_eq!(append_item("", "milk", false), "- [ ] milk");
         assert_eq!(append_item("\n\n", "milk", false), "- [ ] milk");