Add successful experiment cleanup template

What does this MR do?

Adds successful experiment template for cleanup - contributing to gitlab-org/growth/team-tasks#235 (closed)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Contributes to gitlab-org/growth/team-tasks#235 (closed)

Closes https://gitlab.com/gitlab-org/growth/experimentation/-/issues/6

.gitlab/issue_templates/Experiment Successful Cleanup.md

@@ -7,6 +7,8 @@ This now needs to work as it does as part of the product.
 
 ## Steps
 
+- [ ] Determine whether the feature should apply to SaaS and/or self-managed
+- [ ] Determine whether the feature should apply to EE - and which tiers - and/or Core
 - [ ] Determine if tracking should be kept as is, removed or modified.
 - [ ] Migrate experiment to a default enabled [feature flag](https://docs.gitlab.com/ee/development/feature_flags/development.html) for one milestone and add a changelog.
 - [ ] Ensure any relevant documentation has been updated.