switched pip packages to conda-forge

Author: scottyhq

repo2docker/buildpacks/conda/environment.yml

@@ -4,6 +4,5 @@ dependencies:
   - jupyterlab==0.35.4
   - nbconvert==5.4.1
   - notebook==5.7.8
-  - pip:
-    - nteract_on_jupyter==2.0.12
-    - jupyterhub==1.0.*
+  - jupyterhub=1.0.*
+  - nteract_on_jupyter=2.0.12