Add step to fetch asset addresses in nitro-node playbook (#15)

Part of [Service Provider Setup](https://www.notion.so/Service-provider-setup-a09e2207e1f34f3a847f7ce9713b7ac5)

Co-authored-by: Adw8 <adwaitgharpure@gmail.com>
Reviewed-on: cerc-io/testnet-ops#15

nitro-nodes-setup/run-nitro-nodes.yml

@@ -115,3 +115,8 @@
       get_url:
         url: https://git.vdb.to/cerc-io/testnet-laconicd-stack/raw/branch/main/ops/stage2/nitro-node-config.yml
         dest: "{{ nitro_directory }}"
+
+    - name: Fetch required asset addresses
+      get_url:
+        url: https://git.vdb.to/cerc-io/testnet-laconicd-stack/raw/branch/main/ops/stage2/assets.json
+        dest: "{{ nitro_directory }}"