ImplicitlyAllowedValuesPageQueryBuilder switch the document dirty flag

Which does not make any sense for what is supposed to be a read operation.

ImplicitlyAllowedValuesPageQueryBuilder#build set a page related id and value fields. While it does clone the PageClass instance to avoid fully modifying the document, the clone (in this version of XWiki) does not remove the owner document from the element (and if it did it would make the method fail later since it cannot really work without an owner document...).