Update GH CI workflow to conditionally run migrations

Author: letam

.github/workflows/fly-deploy.yml

@@ -23,6 +23,11 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: superfly/flyctl-actions/setup-flyctl@master
-      - run: flyctl ssh console -C 'python manage.py migrate'
+      - run: |
+          # if /data is present, then it is implied that we are using a storage volume, and we should run migrations
+          if [ -d "/data" ]; then
+            flyctl ssh console -C 'python manage.py migrate'
+          fi
+        shell: bash
         env:
           FLY_API_TOKEN: ${{ secrets.FLY_API_TOKEN }}