book: moved overview into architecture

doc/src/SUMMARY.md

@@ -3,13 +3,13 @@
 [DarkFi](README.md)
 - [Ideology](IDEOLOGY.md)
 - [Development](development.md)
-- [Overview](overview/overview.md)
-  - [Anonymous Assets](overview/anonymous_assets.md)
 - [Tutorial](tutorial/tutorial.md)
   - [ZK explainer](tutorial/zk_explainer.md)
 - [Architecture](architecture/architecture.md)
+  - [Overview](overview/overview.md)
   - [Blockchain](architecture/blockchain.md)
   - [DNA](architecture/dna.md)
+  - [Anonymous Assets](overview/anonymous_assets.md)
 - [Client](clients/clients.md)
   - [darkfid JSON-RPC API](clients/darkfid_jsonrpc.md)
   - [cashierd JSON-RPC API](clients/cashierd_jsonrpc.md)