Revert "explicitly update notebook"

This reverts commit 5f0f279.

.github/workflows/build_test_notebooks.yml

@@ -21,15 +21,10 @@ jobs:
           path: ./stingray
           submodules: true
 
-      - name: Update notebooks submodule
-        run: |
-          cd ./stingray
-          git submodule update --init --recursive notebooks
-
       - name: Checkout PR version of notebooks
         if: github.event_name == 'pull_request'
         run: |
-          cd ./stingray/notebooks
+          cd ./stingray/notebooks  # Change to the submodule directory
           git fetch origin pull/${{ github.event.pull_request.number }}/head:PR_${{ github.event.pull_request.number }}
           git checkout PR_${{ github.event.pull_request.number }}
       - name: Setup Python