Update GHA for new Poetry version

Author: encukou

.github/workflows/main.yml

@@ -26,7 +26,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install poetry
-        poetry install
+        poetry install --no-root
     - name: Freeze the site
       run: |
         export NAUCSE_MAIN_REPO_URL=https://github.com/$GITHUB_REPOSITORY