Manually apply JQuery fix for XSS bug (#9521)

This addresses the XSS issue reported in JQuery bug #9521 and fixed in https://github.com/jquery/jquery/commit/db9e023e62c1ff5d8f21ed9868ab6878da2005e9.
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I noticed the copy of JQuery in the RDoc generator contains a known XSS security vulnerability that was fixed in JQuery mainline.  It's a single character fix so rather than updating to the newest version of JQuery, it's easy enough just to patch the code to eliminate the.  Simple enough but if you prefer a discussion on ruby-dev, I am happy to initiate it.