Fix broken external links (round 2)

doc/development/multi_version_compatibility.md

doc/development/new_fe_guide/development/performance.md

doc/development/secure_coding_guidelines.md

doc/development/testing_guide/index.md

doc/development/testing_guide/review_apps.md

doc/gitlab-basics/start-using-git.md

doc/install/azure/index.md

doc/install/requirements.md

doc/integration/vault.md

doc/ssh/README.md

doc/topics/authentication/index.md

doc/topics/autodevops/stages.md

doc/topics/web_application_firewall/index.md

doc/topics/web_application_firewall/quick_start_guide.md

doc/university/README.md

doc/university/support/README.md

doc/user/clusters/applications.md

doc/user/compliance/license_compliance/index.md

doc/user/group/saml_sso/index.md

doc/user/group/saml_sso/scim_setup.md