[FrameworkBundle] add missing attribute to XSD

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | 
| License       | MIT
| Doc PR        | 

The ``hinclude_default_template`` configuration option couldn't have been set in XML configurations since it wasn't defined in the XML schema definition.