[web-animations-1][meta] fix markup

Author: tabatkins

web-animations-1/Overview.bs

@@ -1726,11 +1726,11 @@ for <var>animation</var> defined below:
 
     <div class="switch">
 
-    :   If [=playback rate=] &gt; 0,</dt>
-    ::  Let <var>limit</var> be <a>associated effect end</a>.</dd>
+    :   If [=playback rate=] &gt; 0,
+    ::  Let <var>limit</var> be <a>associated effect end</a>.
 
     :   Otherwise,
-    ::  Let <var>limit</var> be zero.</dd>
+    ::  Let <var>limit</var> be zero.
 
     </div>
 
@@ -3826,7 +3826,7 @@ follows:
     <a lt="value addition">addition operation</a> is defined
     such that it is not commutative, the order of the operands is
     <code><a>underlying value</a> + <a>effect value</a></code>.
-:   <dfn lt="composite operation accumulate">accumulate</dfn></dt>
+:   <dfn lt="composite operation accumulate">accumulate</dfn>
 ::  The <a>effect value</a> is <a
     lt="value accumulation">accumulated</a>
     onto the <a>underlying value</a>.