MAGETWO-94175: Disable backups by default

Author: StasKozar

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

@@ -10,7 +10,7 @@
         <section id="system">
             <group id="backup" translate="label" type="text" sortOrder="500" showInDefault="1" showInWebsite="0" showInStore="0">
                 <label>Backup Settings</label>
-                <field id="functionality_enabled" translate="label" type="select" sortOrder="5" showInDefault="1" showInWebsite="0" showInStore="0">
+                <field id="functionality_enabled" translate="label comment" type="select" sortOrder="5" showInDefault="1" showInWebsite="0" showInStore="0">
                     <label>Enable Backup</label>
                     <comment>Disabled by default for security reasons</comment>
                     <source_model>Magento\Config\Model\Config\Source\Yesno</source_model>