google_login: set a read permission on google secret key property

bt5/erp5_oauth_google_login/PropertySheetTemplateItem/portal_property_sheets/GoogleOAuthPreference/preferred_google_secret_key_property.xml

@@ -32,6 +32,10 @@
             <key> <string>preference</string> </key>
             <value> <int>1</int> </value>
         </item>
+        <item>
+            <key> <string>read_permission</string> </key>
+            <value> <string>Manage portal</string> </value>
+        </item>
       </dictionary>
     </pickle>
   </record>