Add steps to update testnet2 deployments (#38)

Part of [Create a public laconicd testnet](https://www.notion.so/Create-a-public-laconicd-testnet-896a11bdd8094eff8f1b49c0be0ca3b8)

Added steps to update deployments:
- stage2 laconicd
- laconic-console-testnet2
- laconic-shopify
- fixturenet-eth
- Nitro bridge
- Nitro nodes
- Snowball backend
- Snowball frontend

Co-authored-by: Adw8 <adwaitgharpure@gmail.com>
Reviewed-on: cerc-io/testnet-laconicd-stack#38
Co-authored-by: Prathamesh Musale <prathamesh.musale0@gmail.com>
Co-committed-by: Prathamesh Musale <prathamesh.musale0@gmail.com>

testnet-nitro-node.md

@@ -851,6 +851,30 @@ Perform swaps using a swap channel created with another Nitro node over the mirr
   # ]
   ```
 
+## Update nitro nodes
+
+* Switch to deployments dir:
+
+  ```bash
+  cd $DEPLOYMENTS_DIR/nitro-node
+  ```
+
+* Rebuild containers:
+
+  ```bash
+  laconic-so --stack ~/cerc/nitro-stack/stack-orchestrator/stacks/nitro-node build-containers --force-rebuild
+  ```
+
+* Restart the nodes
+
+  ```bash
+  laconic-so deployment --dir l1-nitro-deployment stop
+  laconic-so deployment --dir l1-nitro-deployment start
+
+  laconic-so deployment --dir l2-nitro-deployment stop
+  laconic-so deployment --dir l2-nitro-deployment start
+  ```
+
 ## Clean up
 
 * Switch to deployments dir: