Docs: Fix link to the <code> element specification in HTML5

Author: Golmote

index.html

@@ -137,7 +137,7 @@ <h1>Basic usage</h1>
 &lt;/html></code></pre>
 
 	<p>Prism does its best to encourage good authoring practices. Therefore, it only works with <code>&lt;code></code> elements, since marking up code without a <code>&lt;code></code> element is semantically invalid.
-	<a href="http://www.w3.org/TR/html5/text-level-semantics.html#the-code-element">According to the HTML5 spec</a>, the recommended way to define a code language is a <code>language-xxxx</code> class, which is what Prism uses.
+	<a href="https://www.w3.org/TR/html52/textlevel-semantics.html#the-code-element">According to the HTML5 spec</a>, the recommended way to define a code language is a <code>language-xxxx</code> class, which is what Prism uses.
 	To make things easier however, Prism assumes that this language definition is inherited. Therefore, if multiple <code>&lt;code></code> elements have the same language, you can add the <code>language-xxxx</code> class on one of their common ancestors.
 	This way, you can also define a document-wide default language, by adding a <code>language-xxxx</code> class on the <code>&lt;body></code> or <code>&lt;html></code> element.