Remove unnecessary description

Author: Jihye Hong

css-nav-1/Overview.bs

@@ -1266,7 +1266,6 @@ The meaning of each factor in the function is as follows:
 <dl dfn-type="value" dfn-for="spatial-navigation-distance-function">
     <dt><var>euclidian</var>
     <dd>The euclidian distance between <var>P1</var> and <var>P2</var>
-    <dd>Defined as <pre class="prod">sqrt(pow(<var>P1</var>, 2) + pow(<var>P2</var>, 2))</pre>
 
     <dt><var>alignment</var>
     <dd>The degree of alignment in <var>dir</var> between <var>searchOrigin</var> and <var>candidate</var>