fix(docs): make FCC architecture diagram TB for readability

Author: nikerzetic-aflabs

docs/fcc/1-overview.mdx

@@ -43,7 +43,7 @@ Stay tuned for that and the upcoming guides.
 ## Architecture
 
 ```mermaid
-graph LR
+graph TB
 
     subgraph FCCSystem["FCC System"]
         FC["<b>FCC Contracts</b>