output: Don't add @generated notice to subtemplates

There's already a notice at the top of the file, it doesn't need to be
in subtemplates.

Fixes #158.

blueprintcompiler/outputs/xml/__init__.py

@@ -375,7 +375,7 @@ class XmlOutput(OutputFormat):
             xml.end_tag()
 
         elif isinstance(extension, ExtListItemFactory):
-            child_xml = XmlEmitter()
+            child_xml = XmlEmitter(generated_notice=False)
             child_xml.start_tag("interface")
             child_xml.start_tag("template", **{"class": extension.gir_class})
             self._emit_object_or_template(extension, child_xml)

tests/samples/gtkcolumnview.ui

@@ -10,11 +10,6 @@ corresponding .blp file and regenerate this file with blueprint-compiler.
     <property name="row-factory">
       <object class="GtkBuilderListItemFactory">
         <property name="bytes"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
-<!--
-DO NOT EDIT!
-This file was @generated by blueprint-compiler. Instead, edit the
-corresponding .blp file and regenerate this file with blueprint-compiler.
--->
 <interface>
   <template class="GtkColumnViewRow"></template>
 </interface>]]></property>
@@ -25,11 +20,6 @@ corresponding .blp file and regenerate this file with blueprint-compiler.
         <property name="factory">
           <object class="GtkBuilderListItemFactory">
             <property name="bytes"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
-<!--
-DO NOT EDIT!
-This file was @generated by blueprint-compiler. Instead, edit the
-corresponding .blp file and regenerate this file with blueprint-compiler.
--->
 <interface>
   <template class="GtkColumnViewCell">
     <property name="child">

tests/samples/list_factory.ui

@@ -10,11 +10,6 @@ corresponding .blp file and regenerate this file with blueprint-compiler.
     <property name="factory">
       <object class="GtkBuilderListItemFactory" id="list_item_factory">
         <property name="bytes"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
-<!--
-DO NOT EDIT!
-This file was @generated by blueprint-compiler. Instead, edit the
-corresponding .blp file and regenerate this file with blueprint-compiler.
--->
 <interface>
   <template class="GtkListItem">
     <property name="child">

tests/samples/subscope.ui

@@ -8,11 +8,6 @@ corresponding .blp file and regenerate this file with blueprint-compiler.
   <requires lib="gtk" version="4.0"/>
   <object class="GtkBuilderListItemFactory">
     <property name="bytes"><![CDATA[<?xml version="1.0" encoding="UTF-8"?>
-<!--
-DO NOT EDIT!
-This file was @generated by blueprint-compiler. Instead, edit the
-corresponding .blp file and regenerate this file with blueprint-compiler.
--->
 <interface>
   <template class="GtkListItem">
     <property name="child">