Resolve "Update documentation on virtual env. for Alpha"

• fixed example for pytorch/torchvision in venv
• add workspace creation for venv in example
• add hint for workspaces and venv in general
• quick fix for deprecated JH section

Closes #533 (closed)

doc.zih.tu-dresden.de/docs/jobs_and_resources/alpha_centauri.md

@@ -171,7 +171,7 @@ additional Python packages and create an isolated runtime environment. We recomm
 [JupyterHub](../access/jupyterhub.md) can be used to run Jupyter notebooks on Alpha Centauri
 cluster. You can either use the
 [standard profiles for Alpha](../access/jupyterhub.md/#standard-profiles) or use the advanced form
-and define the resources for your JupyterHub job. The "Alpha GPU (NVIDIA Ampere A100)" Preset
+and define the resources for your JupyterHub job. The "Alpha GPU (NVIDIA Ampere A100)" preset
 is a good starting configuration.
 
 ### Containers