Revert "[DS-1502] Don't let XSL-T decode entities that we wrote inside <script> tags"

This reverts commit 1d8838baa0572ca3038544aaa11820537086a65a.

That commit produces invalid Javascript.  Multiple layers of XML
processing makes it extremely difficult to shepherd a left broket
through the entire pipeline.  Give up on XHTML correctness for now and
revisit some other day.