Update .gitlab-ci.yml

1 job for master in 6 minutes and 21 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
failed #2021
Docker
Linux client build

00:06:21

 
Name Stage Failure
failed
Linux client build Build
Setting up npm (5.8.0+ds6-4) ...
Processing triggers for mime-support (3.62) ...
Processing triggers for libc-bin (2.28-10) ...
$ git clone https://git.khaganat.net/deed/khaganat-web.git
Cloning into 'khaganat-web'...
$ cd khaganat-web
$ pipenv --three update
/bin/bash: line 91: pipenv: command not found
ERROR: Job failed: exit code 1