[css-animations-1] Fix indentiation of deleteRule section

See #4120.

Author: birtles

css-animations-1/Overview.bs

@@ -1157,9 +1157,10 @@ The <code>appendRule</code> method</h4>
 <h4 id="interface-csskeyframesrule-deleterule">
 The <code>deleteRule</code> method</h4>
 
-	The <dfn method for="CSSKeyframesRule" lt="deleteRule(select)">deleteRule</dfn> method deletes the
-    last declared {{CSSKeyframeRule}} matching the specified keyframe selector.
-    If no matching rule exists, the method does nothing.
+The <dfn method for="CSSKeyframesRule" lt="deleteRule(select)">deleteRule</dfn> method
+deletes the last declared {{CSSKeyframeRule}}
+matching the specified keyframe selector.
+If no matching rule exists, the method does nothing.
 
 	Parameters: