Reference common def see_also in element.yaml

Author: Fernando-A-Rocha

schemas/element.yaml

@@ -13,12 +13,4 @@ properties:
     type: string
     description: Description of the element.
   see_also:
-    type: array
-    description: |
-      A list of other categories for further reading.
-      Every element will implicitly display it's own category in *See Also*, unless you
-      introduce this property, then you have to be explicit about it.
-    items:
-      type: string
-      pattern: "^(category):"
-      uniqueItems: true
+    $ref: 'common-defs.yaml#/$defs/see_also'