Run cargo +nightly fix --clippy -Z unstable-options

crates/test_utils/src/lib.rs

@@ -279,7 +279,7 @@ pub fn find_mismatch<'a>(expected: &'a Value, actual: &'a Value) -> Option<(&'a
                 return Some((expected, actual));
             }
 
-            l.values().zip(r.values()).filter_map(|(l, r)| find_mismatch(l, r)).nth(0)
+            l.values().zip(r.values()).filter_map(|(l, r)| find_mismatch(l, r)).next()
         }
         (&Null, &Null) => None,
         // magic string literal "{...}" acts as wildcard for any sub-JSON