Try to enforce npm registry

It has been unstable to download the dpl-design-system during the Github
workfloww that creates releases on branch changes.
This seems to be, at least temporary, a fix.

.github/workflows/create-release-on-branch-changes.yml

@@ -45,7 +45,10 @@ jobs:
           cache: 'yarn'
           registry-url: 'https://npm.pkg.github.com'
 
-      - run: yarn install --frozen-lockfile
+      - name: Install dependencies
+        run: |
+          yarn config set registry https://npm.pkg.github.com
+          yarn install --frozen-lockfile
 
       - name: Build artifacts
         run: yarn build