pin the jupyter hub and lab versions via conda

optional MR in case we really need to specify these versions

environment.yml

@@ -28,10 +28,12 @@ dependencies:
     - pyscal
     - sqsgenerator
     - pymatgen
-    # the following three should be already included with the base image
-    - runner
+    #
+    - jupyterhub=2.3
+    - jupyterlab=3.2.9
     - ipykernel
     - ipympl
+    - runner
     # build tools necessary for ace:
     - make
     - cmake