highlighter: remove redundant (?) call to $.show()

I don't understand why this would be necessary -- the element's just
been created, no style is (presumably) changing its display to anything
other than the default... -- and when highlighting all text in a 5000×3
table, $.show() accounts for 10s out of the 14s it takes to draw the
highlights.

$.show() being absurdly slow is a known problem:
jquery/jquery.com#88

src/ui/highlighter.js

@@ -34,7 +34,7 @@ function highlightRange(normedRange, cssClass) {
         var node = nodes[i];
         if (!white.test(node.nodeValue)) {
             results.push(
-                $(node).wrapAll(hl).parent().show()[0]
+                $(node).wrapAll(hl).parent()[0]
             );
         }
     }