Fix IRI pattern syntax in ShExC: wrong absolute IRIs

[DaniFdezAlvarez]

Current output style:

:Person [http://example.org/ns1#~] AND { foaf:name xsd:string ; rdf:type [foaf:Person]
}

:Document [http://example.org/ns2#~] AND { foaf:title xsd:string ; rdf:type [foaf:Document]
}