fix: typo and better UX when deploying

.github/workflows/cd-deploy-nodes-gcp.yml

@@ -30,9 +30,13 @@ on:
   workflow_dispatch:
     inputs:
       network:
-        default: 'Mainnet'
+        default: Mainnet
         description: 'Network to deploy: Mainnet or Testnet'
         required: true
+        type: choice
+        options:
+          - Mainnet
+          - Testnet
       cached_disk_type:
         default: tip
         description: 'Type of cached disk to use'
@@ -194,7 +198,7 @@ jobs:
       network: ${{ inputs.network || vars.ZCASH_NETWORK }}
       disk_prefix: zebrad-cache
       disk_suffix: ${{ inputs.cached_disk_type || 'tip' }}
-      prefer_main_cached_state: (github.event_name == 'push' && github.ref_name == 'main' && true) || false
+      prefer_main_cached_state: ${{ (github.event_name == 'push' && github.ref_name == 'main' && true) || false }}
 
   # Deploy Managed Instance Groups (MiGs) for Mainnet and Testnet,
   # with one node in the configured GCP region.