Remove flakey separation in GitLab CI

We already removed the flakey separation in the gulp code in https://gitlab.com/gitlab-org/gitter/webapp/-/merge_requests/1926
and forgot to remove the separation here.
12 jobs for !1998 with no-more-test-separation in 27 minutes and 12 seconds (queued for 1 second)
detached
Status Job ID Name Coverage
  Build Unit Test
passed #689931251
gitlab-org
package

00:06:43

passed #689931245
gitlab-org
test

00:12:31

manual #689931249
internal allowed to fail manual
test_e2e
passed #689931243
gitlab-org
validate

00:05:23

 
  Pre Deploy
passed #689931255
gitlab-org
distribute_beta_staging

00:00:38

 
  Deploy
passed #689931258
gitlab-org-docker
containerize

00:07:22

manual #689931260
internal allowed to fail manual
deploy_beta_staging
 
  Security
passed #689931269
gitlab-org
container_scanning

00:01:06

passed #689931265
gitlab-org
dast

00:06:39

passed #689931267
gitlab-org-docker
dependency_scanning

00:05:37

passed #689931263
gitlab-org-docker
sast

00:02:50

passed #689931272
gitlab-org-docker
secret_detection

00:00:32