Use hardcoded value for PropType secret

Author: Brandon Dail

Diff for: src/isomorphic/classic/types/ReactPropTypesSecret.js

@@ -13,6 +13,6 @@
 'use strict';
 
 
-const ReactPropTypesSecret = '__REACT_PROP_TYPES_SECRET__' + Math.random().toString();
+const ReactPropTypesSecret = 'REACT_PROPTYPES_CALL_SECRET';
 
 module.exports = ReactPropTypesSecret;