Redundant namespace declarations

A namespace prefix declared on the xsl:stylesheet element but never used by any element name, attribute name, or qualified name inside an attribute value is dead weight that misleads the reader and should be removed.

Incorrect:

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:foo="urn:foo" version="2.0">
  <!-- the foo prefix is never used anywhere -->
</xsl:stylesheet>

Correct:

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="2.0">
  <!-- only namespaces that are actually used are declared -->
</xsl:stylesheet>