[css-display] 3-keyword value of display are also at risk. Fixes #1490.

Author: tabatkins

css-display/Overview.bs

@@ -17,7 +17,7 @@ Abstract: This module describes how the CSS formatting box tree is generated fro
 Ignored Terms: display-model, display-role, table row group box, absolutely positioned, table formatting context
 At Risk: Application of ''::first-letter'' in the presence of run-ins
 At Risk: ''display: run-in''
-At Risk: All two-keyword values of 'display' and ''display: inline-list-item''
+At Risk: All multi-keyword values of 'display' and ''display: inline-list-item''
 </pre>
 <pre class="link-defaults">
 spec:css-break-3; type:dfn; text:fragment;