fix: internal symbol method is now really a symbol

Author: panva

lib/help/symbols.js

@@ -2,3 +2,4 @@ module.exports.KEYOBJECT = Symbol('KEYOBJECT')
 module.exports.PRIVATE_MEMBERS = Symbol('PRIVATE_MEMBERS')
 module.exports.PUBLIC_MEMBERS = Symbol('PUBLIC_MEMBERS')
 module.exports.THUMBPRINT_MATERIAL = Symbol('THUMBPRINT_MATERIAL')
+module.exports.JWK_MEMBERS = Symbol('JWK_MEMBERS')