[README] Adjusting dropdown box for the older versions..

Author: Murilo Marinho

docs/README.md

@@ -164,13 +164,17 @@ The PPA for the LGPL version is available at https://smartarmstack.github.io/sma
 
 The PPA for the CC-BY-NC version is available at https://marinholab.github.io/sas_debian_builder_noncommercial/. The archive is currently private. 
 
-## Older versions
+```{note}
+:class: dropdown
+# Older (and unsupported) versions
 
-Older (and unsupported) versions are available at:
 - https://github.com/SmartArmStack/smart_arm_stack
 - https://github.com/SmartArmStack/smart_arm_stack_lgpl
 - https://github.com/SmartArmStack/smart_arm_stack_researchonly
 
+:::
+```
+
 ## Acknowledgements
 
 ```{figure} img/computer_capi_open_tech.png