resolve_message_name_conflict_with_field_name is now a Shadow case

we change the test as this is not a proper case

prost-reflect/src/descriptor/tests.rs

@@ -146,15 +146,8 @@ fn resolve_message_name_conflict_with_field_name() {
         }],
     };
 
-    let descriptor_pool = DescriptorPool::from_file_descriptor_set(file_descriptor_set).unwrap();
-    let message = descriptor_pool
-        .get_message_by_name("my.package.MyMessage")
-        .unwrap();
-    let field = message.get_field_by_name("MyMessage").unwrap();
-    assert_eq!(
-        field.kind().as_message().unwrap().full_name(),
-        "my.package.MyMessage"
-    );
+    let e = DescriptorPool::from_file_descriptor_set(file_descriptor_set).unwrap_err();
+    assert_eq!(e.to_string(), "name 'MyMessage' is shadowed");
 }
 
 #[test]