Update main.yml

use nbdev 1

.github/workflows/main.yml

@@ -11,7 +11,7 @@ jobs:
         architecture: 'x64'
     - name: Install the library
       run: |
-        pip install nbdev jupyter
+        pip install nbdev==1.2.5 jupyter
         pip install -e .
     - name: Read all notebooks
       run: |