deploy: fix: must be nested

.forgejo/workflows/push.yaml

@@ -12,7 +12,6 @@ jobs:
     if: contains(github.event.head_commit.message, 'deploy:')
     steps:
       - uses: https://code.forgejo.org/actions/checkout@v3
-      - run: nix develop
       - name: Setup SSH key
         run: |
           mkdir -p ~/.ssh
@@ -20,4 +19,6 @@ jobs:
           chmod 600 ~/.ssh/id_rsa
         env:
           SSHKEY: ${{ secrets.SSHKEY }}
-      - run: deploy
+      - run: |
+          nix develop &&
+          deploy