Remove xsl:output and omit-xml-declaration element, because it

Remove xsl:output and omit-xml-declaration element, because it
seems to be causing problems with xsltproc. Closes bug #1785732.
Thanks to Denis Gillain for reporting.
I remember that the reason I added this originally was to work
around some other but in xsltproc (I think it was that it was
emitting an xml declaration even when output method is set to
text, or something) so this change is going to probably going to
cause a regression of that, but oh well