Ensure Geo QA is passing on Staging Ref Geo sites

With the work from Set up GitLab-QA pipeline for the new Staging R... (#350870 - closed), Staging Ref now has Geo QA schedule and it uses Test::Instance::StagingRefGeo scenario. Currently notifications are not configured to reduce the noise as job constantly fails. Example of Geo QA job against Staging Ref:

• Job: https://ops.gitlab.net/gitlab-org/quality/staging-ref/-/jobs/6925492
  • Result: 26 examples, 8 failures, 1 pending

This issue is to further improve Geo QA job and ensure it's passing:

• Investigate failures from Geo QA pipeline. To get latest results, trigger Daily Geo tests schedule in https://ops.gitlab.net/gitlab-org/quality/staging-ref/-/pipeline_schedules
• Fix the issues that were found and ensure that pipeline is green
• Configure and enable Slack notification for Geo QA pipeline in #qa-staging-ref
• Activate Daily Geo tests schedule
• Announce in Quality channel that Geo QA tests will run regularly now