tags inside noscript block are escaped

Problem/Motivation

Pasted HTML into the edit box in Plain Text mode, thus:

<noscript><br/><span id="warning">You must have JavaScript enabled to use this feature.</span></noscript>

then changed to Full HTML. When I changed back to Plain Text to paste more HTML, I noticed that the noscript block was now:

<noscript>&amp;amp;amp;amp;amp;lt;br/&amp;amp;amp;amp;amp;gt;&amp;amp;amp;amp;amp;lt;span id="warning"&amp;amp;amp;amp;amp;gt;You must have JavaScript enabled to use this feature.&amp;amp;amp;amp;amp;lt;/span&amp;amp;amp;amp;amp;gt;</noscript>

Proposed resolution

Nested tags are allowed within a noscript block, so don't repeatedly encode tags within a noscript block.