adapter.xml: Remove <aas:kind> from SubmodelElements in XSD

Version 3.0 of the spec removes the attribute `kind` from
`SubmodelElement`s.
While we already implemented this, it was still missing in the
XSD Schema, as well as the examples. This commit fixes that.

Author: s-heppner

basyx/aas/adapter/xml/AAS.xsd

@@ -862,7 +862,6 @@
   <xs:group name="submodelElement">
     <xs:sequence>
       <xs:group ref="referable"/>
-      <xs:group ref="hasKind"/>
       <xs:group ref="hasSemantics"/>
       <xs:group ref="qualifiable"/>
       <xs:group ref="hasDataSpecification"/>