Disable application settings cache in GDK tests

What does this MR do and why?

Disables the application settings cache in GDK tests, as we do for e2e tests against omnibus-gitlab (see !51889 (merged))

Should fix #419206 (closed)

How to set up and validate locally

To avoid the need to build the GDK image locally, you can use one built in this MR to confirm that the setting has the expected value:

docker run --rm --entrypoint=/bin/bash \
  registry.gitlab.com/gitlab-org/gitlab/gitlab-qa-gdk:ml-gdk-disable-application-settings-cache \
  -c "cat gitlab/config/gitlab.yml | grep application_settings_cache_seconds"
Unable to find image 'registry.gitlab.com/gitlab-org/gitlab/gitlab-qa-gdk:ml-gdk-disable-application-settings-cache' locally
ml-gdk-disable-application-settings-cache: Pulling from gitlab-org/gitlab/gitlab-qa-gdk
...
Status: Downloaded newer image for registry.gitlab.com/gitlab-org/gitlab/gitlab-qa-gdk:ml-gdk-disable-application-settings-cache
    application_settings_cache_seconds: 0

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.