Use elementType for stepTemplate

Author: rvsia

packages/pf4-component-mapper/src/files/wizard.js

@@ -160,7 +160,7 @@ WizardInternal.propTypes = {
   hasNoBodyPadding: PropTypes.bool,
   navAriaLabel: PropTypes.string,
   container: PropTypes.instanceOf(Element),
-  StepTemplate: PropTypes.func
+  StepTemplate: PropTypes.elementType
 };
 
 const defaultLabels = {