Merge branch 'docs/ssot_custom_project_templates' into 'master'

Edited "Custom group-level project templates" for SSOT

See merge request gitlab-org/gitlab-ce!29235

doc/user/group/custom_project_templates.md

+---
+type: reference
+---
+
 # Custom group-level project templates **[PREMIUM]**
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab-ee/issues/6861) in [GitLab Premium](https://about.gitlab.com/pricing) 11.6.
@@ -24,3 +28,15 @@ Projects of nested subgroups of a selected template source cannot be used.
 
 Repository and database information that are copied over to each new project are
 identical to the data exported with [GitLab's Project Import/Export](../project/settings/import_export.md).
+
+<!-- ## Troubleshooting
+
+Include any troubleshooting steps that you can foresee. If you know beforehand what issues
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+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
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+
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+If you have none to add when creating a doc, leave this section in place
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