Merge branch 'docs/ssot_cicd_settings' into 'master'

Edit CI/CD settings for SSOT guidelines

See merge request gitlab-org/gitlab-ce!28582

doc/user/admin_area/settings/continuous_integration.md

+---
+type: reference
+---
+
 # Continuous Integration and Deployment Admin settings **[CORE ONLY]**
 
 In this area, you will find settings for Auto DevOps, Runners and job artifacts.
@@ -145,3 +149,15 @@ To set the duration for which the jobs will be considered as old and expired:
 Once that time passes, the jobs will be archived and no longer able to be
 retried. Make it empty to never expire jobs. It has to be no less than 1 day,
 for example: <code>15 days</code>, <code>1 month</code>, <code>2 years</code>.
+
+<!-- ## Troubleshooting
+
+Include any troubleshooting steps that you can foresee. If you know beforehand what issues
+one might have when setting this up, or when something is changed, or on upgrading, it's
+important to describe those, too. Think of things that may go wrong and include them here.
+This is important to minimize requests for support, and to avoid doc comments with
+questions that you know someone might ask.
+
+Each scenario can be a third-level heading, e.g. `### Getting error message X`.
+If you have none to add when creating a doc, leave this section in place
+but commented out to help encourage others to add to it in the future. -->
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