MC-15763: Introduce critical CSS scope loaded through head

- Stabilization

Author: vzabaznov

app/code/Magento/Theme/etc/adminhtml/system.xml

@@ -13,7 +13,7 @@
                     <label>Use CSS critical path</label>
                     <source_model>Magento\Config\Model\Config\Source\Yesno</source_model>
                     <comment>
-                        <![CDATA[<strong style="color:red">Warning!</strong> Be sure that you have critical.css file for your theme. Other CSS files will be loaded asynchronously]]>
+                        <![CDATA[<strong style="color:red">Warning!</strong> Be sure that you have critical.css file for your theme. Other CSS files will be loaded asynchronously.]]>
                     </comment>
                 </field>
             </group>