Fix regexp in \s sed in Kubernetes tutorial

[LeonardAukea]

This PR updates the regexp to its intended behaviour. that is to not drop the last character in the folder names.

ls -d */ | sed 's/.$//'                                                   
fronten
infr
kitche
mo
prox

=>

$ ls -d */ | sed 's/$.//'                                                 
frontend
infra
kitchen
mon
proxy

Closes: #1767

[mvdan]

cc @myitcv who I seem to recall was doing a bit of a refactor on this tutorial

[mvdan]

Given that we've closed the original issue as a minor issue on the user's side, I'm inclined to not apply this change, given that the shell line appears to be working for everyone with the standard ls tool :) Please let me know if you still think we should merge this.