Use arbitrary componentIdentity

There was no particular reason it was set to element.type. We just wanted to check if something is a render phase update.

packages/react-test-renderer/src/ReactShallowRenderer.js

@@ -560,7 +560,8 @@ class ReactShallowRenderer {
       } else {
         const prevDispatcher = ReactCurrentDispatcher.current;
         ReactCurrentDispatcher.current = this._dispatcher;
-        this._prepareToUseHooks(element.type);
+        const componentIdentity = {};
+        this._prepareToUseHooks(componentIdentity);
         try {
           if (isForwardRef(element)) {
             this._rendered = element.type.render(element.props, element.ref);