[web-animations-1] Fix broken links to CSS Properties and Values API

Author: birtles

web-animations-1/Overview.bs

@@ -194,6 +194,9 @@ urlPrefix: https://drafts.csswg.org/css-style-attr/; type: dfn; spec: css-style-
 urlPrefix: https://drafts.csswg.org/web-animations-2/; type: dfn; spec: web-animations-2
     text: iteration composite operation
     text: iteration composite operation accumulate
+urlPrefix: https://drafts.css-houdini.org/css-properties-values-api-1/; type: dfn; spec: css-properties-values-api-1
+    text: syntax definition
+    text: universal syntax definition
 </pre>
 <pre class="link-defaults">
 spec:dom; type:interface; text:DocumentOrShadowRoot
@@ -3179,10 +3182,10 @@ is defined in [[#animation-types]].
 For <a>custom properties</a> registered
 using the {{CSS/registerProperty()}} method for the <a>current global object</a>,
 the <a>animation type</a> is <a>by computed value</a>,
-derived from the type used to define the property's {{PropertyDescriptor/syntax}}.
+derived from the type used in the property's <a>syntax definition</a>.
 Where there is no <a>computed value</a> type that corresponds
-to the property's specified {{PropertyDescriptor/syntax}}
-(e.g. when the syntax is "*")
+to the property's specified syntax
+(e.g. when the syntax is the <a>universal syntax definition</a>)
 or when the <a>custom property</a> is not registered,
 the <a>animation type</a> is <a>discrete</a>.