ObjC: avoid assign for object properties (part 2)
Follow up on https://github.com/protocolbuffers/protobuf/pull/6221
diff --git a/objectivec/GPBDescriptor.h b/objectivec/GPBDescriptor.h
index b6a85c1..331d444 100644
--- a/objectivec/GPBDescriptor.h
+++ b/objectivec/GPBDescriptor.h
@@ -305,7 +305,7 @@
/** Whether the extension is packable. */
@property(nonatomic, readonly, getter=isPackable) BOOL packable;
/** The class of the message if the extension is of message type. */
-@property(nonatomic, readonly, assign) Class msgClass;
+@property(nonatomic, readonly) Class msgClass;
/** The singleton name for the extension. */
@property(nonatomic, readonly) NSString *singletonName;
/** The enum descriptor if the extension is of enum type. */
