Update ExplicitSize mock to match implementation

frontend/src/metabase/components/__mocks__/ExplicitSize.jsx

 /* eslint-disable react/display-name */
 import React from "react";
 
-const ExplicitSize = ComposedComponent => props => (
+const ExplicitSize = measureClass => ComposedComponent => props => (
   <ComposedComponent width={1000} height={1000} {...props} />
 );