Set Append attribute to false by default for structure template

Since NXS-6406 the "append" attribute is added to the definition of a Structure Template (factoryBInding extension point)

Currently the default value for "Deployment mode" is "merge" and then it adds append="true" to the existing definitions :

  <extension target="org.nuxeo.ecm.platform.content.template.service.ContentTemplateService" point="factoryBinding">
    <factoryBinding name="DomainFactory" factoryName="SimpleTemplateFactory" targetType="Domain" append="true">
...

To keep the same behavior as before NXS-6406, the default value for Append should be false (or no append attribute). And the default value for "Deployment mode" in the UI for Structure Templates should be "override" ?