[Misc] Wait for the inplace editor in InplaceTranslateIT

This hopefully fixes flickering that was observed in particular on the
stable-15.10.x branch.

(cherry picked from commit e70de459)

xwiki-platform-core/xwiki-platform-edit/xwiki-platform-edit-test/xwiki-platform-edit-test-docker/src/test/it/org/xwiki/edit/test/ui/InplaceTranslateIT.java

@@ -154,6 +154,7 @@ void translateInplace(TestUtils setup, TestReference testReference)
         viewPage.setDocumentTitle("English Title").save();
         // This changes the document locale.
         viewPage.getTranslateButton().click();
+        viewPage.waitForInplaceEditor();
         assertEquals("English Title", viewPage.getDocumentTitle());
 
         viewPage.setDocumentTitle("title IT").saveAndView();