core: rustfmt splits on fn_call_width, not max_width

Three assertions I had collapsed to one line because they fit inside
max_width=100. rustfmt's fn_call_width is 60 and applies to the ARGUMENT list,
so a call can sit well under the line limit and still be split vertically.
Clippy and the tests were already green; this is the formatter only.

core/src/local/derive.rs

@@ -294,7 +294,10 @@ mod tests {
     #[test]
     fn items_basic() {
         let body = "shopping\n\n- [ ] milk\n- [x] eggs";
-        assert_eq!(extract_items(body), vec![item("milk", false), item("eggs", true)]);
+        assert_eq!(
+            extract_items(body),
+            vec![item("milk", false), item("eggs", true)]
+        );
     }
 
     #[test]
@@ -324,7 +327,10 @@ mod tests {
     fn items_accept_star_bullets_and_indentation() {
         // `*` because markdown.ts already takes it for a plain bullet.
         let body = "* [ ] star\n    - [x] indented";
-        assert_eq!(extract_items(body), vec![item("star", false), item("indented", true)]);
+        assert_eq!(
+            extract_items(body),
+            vec![item("star", false), item("indented", true)]
+        );
     }
 
     #[test]
@@ -350,7 +356,10 @@ mod tests {
     #[test]
     fn checking_addresses_items_not_lines() {
         let body = "note\n- [ ] a\nprose\n- [ ] b";
-        assert_eq!(set_item_checked(body, 1, true), "note\n- [ ] a\nprose\n- [x] b");
+        assert_eq!(
+            set_item_checked(body, 1, true),
+            "note\n- [ ] a\nprose\n- [x] b"
+        );
     }
 
     #[test]