ci: remove dockerhub login for tests

This break tests on forked repositories.

.github/workflows/test.yml

@@ -36,12 +36,6 @@ jobs:
           pip install -r python-requirements.txt
         working-directory: test/requirements
 
-      - name: Login to DockerHub
-        uses: docker/login-action@v3
-        with:
-          username: ${{ secrets.DOCKERHUB_USERNAME }}
-          password: ${{ secrets.DOCKERHUB_TOKEN }}
-
       - name: Pull nginx:alpine image
         run: docker pull nginx:alpine