Add reliable tag to related issues and scoped labels e2e tests

What does this MR do?

Add the reliable tag to related_issues_spec and editing_scoped_labels_spec since they've been passing for the required amount of time.

• gitlab-org/quality/testcases#541 (closed) - passing for 2 weeks
• gitlab-org/quality/testcases#595 (closed) - passing for 1 week

Screenshots

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