Fix misprint in the error message

serde/src/de/value.rs

@@ -1034,7 +1034,7 @@ where
         let value = self.value.take();
         // Panic because this indicates a bug in the program rather than an
         // expected failure.
-        let value = value.expect("MapAccess::visit_value called before visit_key");
+        let value = value.expect("MapAccess::next_value called before next_key");
         seed.deserialize(value.into_deserializer())
     }