CI broken because of shellcheck

[ljupcovangelski]

Shellcheck fails because of the which command

In scripts/bootstrap.sh line 55:
    printf "Vagrant installed in %s\n" "$(which vagrant)"
                                          ^---^ SC2230: which is non-standard. Use builtin 'command -v' instead.
In scripts/bootstrap.sh line 120:
    printf "Virtualbox installed in %s \n" "$(which VBoxManage)"
                                              ^---^ SC2230: which is non-standard. Use builtin 'command -v' instead.

[ljupcovangelski]

Fixed.