Fix JupyterLab spelling

This fails CI otherwise:

access/jupyterlab_user.md Custom JupyterLab != Custom jupyterlab

doc.zih.tu-dresden.de/docs/access/jupyterlab_user.md

-# Custom jupyterlab
+# Custom JupyterLab
 
 Is it now possible to install your custom JupyterLab.
 
@@ -16,7 +16,7 @@ Please understand that JupyterLab is a complex software system of which we are
 not the developers and don't have any downstream support contracts for, so we
 merely offer an installation of it and will not provide additional support.
 
-Start a new jupyterlab session at: [jupyterhub](https://jupyterhub.hpc.tu-dresden.de) as
+Start a new JupyterLab session at: [jupyterhub](https://jupyterhub.hpc.tu-dresden.de) as
 described at: [start session](https://doc.zih.tu-dresden.de/access/jupyterhub/#start-a-session)
 
 ## Prepare the installation