Increase disk requirements and cpu

Hello, I am one of the Renku developers.

I see that some of your students launch sessions from this projects and the sessions crash because there is not enough disk space. Currently you need about 15gb of space if the "lfs autofetch" flag is enabled. So I reccomend that you increase the requirements to at least double that (i.e. 30gb) just to be safe.

Also using 0.25 cpu for the session is not enough. You should increase this to 0.5 or 1. The UI in jupyterlab is very laggy when 0.25 cpus are used. For example in my tests with 0.25 cpus it took almost 5 minutes for me to open a terminal. Whereas with 1 cpu it was instantaneous.