[css-values-5] Fix markup

Author: fantasai

css-values-5/Overview.bs

@@ -1622,9 +1622,9 @@ Ian's proposal:
 
 	<div class='note'>
 		Note that the default value need not be of the type given.
-		For instance, if the type required of the attribute by the author is ''<number px>'',
+		For instance, if the type required of the attribute by the author is ''&lt;number px>'',
 		the default could still be <css>auto</css>,
-		like in ''width: attr(size <number px>, auto);''.
+		like in ''width: attr(size &lt;number px>, auto);''.
 	</div>
 
 	<div class="example">
@@ -1738,7 +1738,7 @@ Security</h4>
 		However, using ''attr()'' for other purposes is fine,
 		even if the usage is <em>near</em> a url:
 
-		* ''background-image: image("foo.jpg", attr(bgcolor <color>))'' is fine;
+		* ''background-image: image("foo.jpg", attr(bgcolor &lt;color>))'' is fine;
 			the ''attr()'' is providing a fallback color,
 			and the <<url>> isn't [=attr()-tainted=].
 	</div>