Update .gitlab-ci.yml

2 jobs for gh-pages in 9 seconds (queued for 2 seconds)
Name Stage Failure
failed
GhPagesJob Test There is an unknown failure, please try again
$ echo test
test
$ echo $cise
ci-se1234567
$ echo testend
testend
$ git clone https://ci-se:${env.cise}@git.rwth-aachen.de/monticore/EmbeddedMontiArc/generators/visualisation --branch gh-pages --single-branch gh_pages
/bin/bash: line 64: https://ci-se:${env.cise}@git.rwth-aachen.de/monticore/EmbeddedMontiArc/generators/visualisation: bad substitution
ERROR: Job failed: exit code 1