ACQE-4418 : Added more assertion

Author: Manjusha

app/code/Magento/Newsletter/Test/Mftf/ActionGroup/StorefrontCreateNewsletterSubscriberActionGroup.xml

@@ -12,6 +12,7 @@
         <arguments>
             <argument name="email" type="string"/>
         </arguments>
+        <waitForElementVisible  selector="{{BasicFrontendNewsletterFormSection.newsletterEmail}}"></waitForElementVisible>
         <fillField stepKey="fillEmailField" selector="{{BasicFrontendNewsletterFormSection.newsletterEmail}}" userInput="{{email}}"/>
         <click selector="{{BasicFrontendNewsletterFormSection.subscribeButton}}" stepKey="submitForm"/>
     </actionGroup>