clean conda in proper place and clean apt cache

    Cleaning conda in separate stage creates two large diffs, that is
    not acceptable.
1 job for master in 13 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Mirror
failed #30521
allowed to fail
mirror repository

00:00:13

 
Name Stage Failure
failed
mirror repository Mirror There is an unknown failure, please try again
Load key "/home/jovyan/.ssh/id_rsa": invalid format
git@github.com: Permission denied (publickey).
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.
Running after script...
$ rm -rf ~/.ssh
ERROR: Job failed: exit code 1