MAGETWO-69480: Critical error appears when user opens CMS page to edit in developer mode

- fix block definition

Author: Igor Melnikov

app/code/Magento/GoogleOptimizer/view/adminhtml/ui_component/cms_page_form.xml

@@ -13,7 +13,7 @@
         </settings>
         <container name="google_experiment_container" sortOrder="250">
             <htmlContent name="html_content">
-                <block name="googleOptimizerBlockAdminhtmlFormCmsPage" class="MagentoGoogleOptimizerBlockAdminhtmlFormCmsPage"/>
+                <block name="googleOptimizerBlockAdminhtmlFormCmsPage" class="Magento\GoogleOptimizer\Block\Adminhtml\Form\CmsPage"/>
             </htmlContent>
         </container>
     </fieldset>