remove jasper2 validateXml attribute as it's causing troubles

default attribute value shall be false anyway

addressing:
/builddir/build/BUILD/spacewalk-java-2.0.2/build.xml:845: The following error occurred while executing this line:
/builddir/build/BUILD/spacewalk-java-2.0.2/build.xml:646: jasper2 doesn't support the validateXml attribute

(cherry picked from commit dd0ef60c26790b94e7ce0bdd9bcc1464baee71cc)
Automatic commit of package [spacewalk-java] release [2.2.126-1].