Fix typo in html5-and-css.json

The challenge "Nest an Anchor Element within a Paragraph" has a small typo at the end of the English description text as highlighted below:

"Now nest your existing a element within a new p element so that the surrounding paragraph says "View more cat photos", but where only "cat photos" is a link, and the rest of the text is rest is plain text."

This commit removes the final "rest is" highlighted above, giving us this sentence instead:

Now nest your existing a element within a new p element so that the surrounding paragraph says "View more cat photos", but where only "cat photos" is a link, and the rest of the text is plain text.

challenges/html5-and-css.json

@@ -1135,7 +1135,7 @@
         "<a href=\"http://i.imgur.com/hviuZwe.png\" data-lightbox=\"img-enlarge\"><img class=\"img-responsive\" title=\"Click to enlarge\" alt=\"a diagram of how anchor tags are composed with the same text as on the following line\" src=\"http://i.imgur.com/hviuZwe.png\"></a>",
         "Here's an example: <code>&#60;p&#62;Here's a &#60;a href=\"http://freecodecamp.com\"&#62; link to Free Code Camp&#60;/a&#62; for you to follow.&#60;/p&#62;</code>.",
         "<code>Nesting</code> just means putting one element inside of another element.",
-        "Now nest your existing <code>a</code> element within a new <code>p</code> element so that the surrounding paragraph says \"View more cat photos\", but where only \"cat photos\" is a link, and the rest of the text is rest is plain text."
+        "Now nest your existing <code>a</code> element within a new <code>p</code> element so that the surrounding paragraph says \"View more cat photos\", but where only \"cat photos\" is a link, and the rest of the text is plain text."
       ],
       "tests": [
         "assert($(\"a\").attr(\"href\").match(/freecatphotoapp.com/gi).length > 0, 'You need an <code>a</code> element that links to \"freecatphotoapp.com\".')",