remove broken link to software policies workshop materials, add "upon request" instead

_posts/2021/05/2021-05-19-software-policies-workshop.md

@@ -37,9 +37,7 @@ breakout sessions.
 
 The results were documented on virtual whiteboards.
 All presentation slides and the result of the virtual whiteboards are made
-available in [Nubes](https://nubes.helmholtz-berlin.de).
-
-<a href="https://nubes.helmholtz-berlin.de/s/MxHb3YmMCKb7q6r" markdown=1>**<i class="fas fa-file-download"></i> &nbsp;Click here to download the material.**</a>{:.btn .btn-primary}
+available in [Nubes](https://nubes.helmholtz-berlin.de) upon request.
 
 ## Future Exchange Process
 All interested Helmholtz stakeholders are very welcome to actively participate