Bump version to 7.15.0

Diff: https://gitlab.com/gitlab-org/gitlab-qa/-/compare/v7.14.0...7bc256614935b01657e8b45b005b87e5beafcb24

Release notes:

• Reflect Docker's UI update (51e66540)

• Disable issue report title updates on certain pipelines (334c3b43)

• Merge branch 'disable-title-update-on-certain-pipelines' into 'master' (db9c48a5)

• Merge branch 'update-docker-pref-hint' into 'master' (9c408206)

• Add env varible config for disabling the Chrome /dev/shm usage (e5688d14)

• Save new knapsack report (6b45d437)

• Merge branch 'ml-save-new-knapsack-report' into 'master' (654dd37c)

• Save gitaly cluster logs to a file (7b303c20)

• Merge branch 'ml-output-gitaly-cluster-logs-to-file' into 'master' (8a87502e)

• Remove knapsack report path (a22edcd2)

• Merge branch 'ml-remove-knapsack-report-path' into 'master' (0561530c)

• Merge branch 'add-disable-devshm-flag' into 'master' (26292ae3)

• Increase test job timeouts to 90 minutes (a7544ba5)

• Merge branch 'shl-increase-job-timeout' into 'master' (39b994a3)

• Doc: Add note about GDK initial password for QA tests (ab452df6)

• Merge branch 'gdk-init-passwd-var' into 'master' (d7b7278b)

• Add Service Ping configuration (1d0d6953)

• Merge branch 'am-add-service-ping-configuration' into 'master' (77dda666)

• Update version to 7.15.0 (7bc25661)

• Checklist before merging:

  • Diff link is up-to-date.
  • Based on the diff, lib/gitlab/qa/version.rb is updated, according to SemVer.
  • Release notes are accurate.

• Checklist after merging:

  • Update the release notes for the newly created tag.