[ci] fix CUDA CI builds (#3549)

.github/workflows/cuda.yml

@@ -38,7 +38,7 @@ jobs:
       - name: Remove old folder with repository
         run: sudo rm -rf $GITHUB_WORKSPACE
       - name: Checkout repository
-        uses: actions/checkout@v2.3.4
+        uses: actions/checkout@v1
         with:
           fetch-depth: 5
           submodules: true
@@ -52,6 +52,7 @@ jobs:
             OS_NAME=linux
             BUILD_DIRECTORY=$ROOT_DOCKER_FOLDER
             CONDA_ENV=test-env
+            PYTHON_VERSION=3.8
             EOF
             cat > docker-script.sh <<EOF
             export CONDA=\$HOME/miniconda