Hard-code formal syntax (#25327)

* Remove formal syntax

Fix #25321

* hard-code formal syntax

Author: dawei-wang

files/en-us/web/css/-moz-float-edge/index.md

@@ -44,7 +44,10 @@ The non-standard **`-moz-float-edge`** [CSS](/en-US/docs/Web/CSS) property speci
 
 ## Formal syntax
 
-{{csssyntax}}
+```plain
+-moz-float-edge =
+  border-box | content-box | margin-box | padding-box
+```
 
 ## Examples