fix broken link

Author: Lauren

v2.1/add-column.md

@@ -10,7 +10,7 @@ The `ADD COLUMN` [statement](sql-statements.html) is part of `ALTER TABLE` and a
 ## Synopsis
 
 <div>
-{% include sql/{{ page.version.version }}/diagrams/add_column.html %}
+{% include {{ page.version.version }}/sql/diagrams/add_column.html %}
 </div>
 
 ## Required privileges