update bounding boxes hint

In 2.5.8 Target Size (Minimum) SC, "bounding box" anchor link does not point to any definition

guidelines/terms/22/minimum-bounding-box.html

@@ -1,4 +1,4 @@
-<dt class="new"><dfn data-lt="bounding boxes">minimum bounding box</dfn></dt>
+<dt class="new"><dfn data-lt="bounding boxes|bounding box">minimum bounding box</dfn></dt>
 <dd class="new">
 	<p class="change">New</p>	
    <p>the smallest enclosing rectangle aligned to the horizontal axis within which all the points of a shape lie. For components which wrap onto multiple lines as part of a sentence or block of text (such as hypertext links), the bounding box is based on how the component would appear on a single line.</p>