BUG: Remmove Binder JupyterLab extension install

We are not yet compatibile with JupyterLab 3, this causes build issues
with dependencies.

Author: thewtex

.binder/postBuild

@@ -6,6 +6,3 @@ pip install .
 # add itkwidgets
 jupyter nbextension install --py --sys-prefix itkwidgets
 jupyter nbextension enable --py --sys-prefix itkwidgets
-cd /tmp/
-jupyter labextension install @jupyter-widgets/jupyterlab-manager
-jupyter labextension install jupyter-matplotlib jupyterlab-datawidgets jupyter-webrtc itkwidgets [email protected] [email protected]