fix ERD diagram

dimitri-yatsenko · dimitri-yatsenko · commit 229ab6322d9d · 2024-09-09T15:29:04.000-05:00
diff --git a/book/20-concepts/01-relational.md b/book/20-concepts/01-relational.md
@@ -231,8 +231,6 @@ erDiagram
 ```
 Entity-relationship diagram in [Crow's Foot notation](https://mermaid.js.org/syntax/entityRelationshipDiagram.html).
 :::
-```
-
 
 :::{figure}
 ```{mermaid}
