WIP: Add _spec suffix to add_design_add_annotation

What does this MR do?

@ddavison @mlapierre raised in 3152cf4b (comment 372680554):

Previously, the file was named add_design_add_annotation.rb without the _spec.rb suffix, meaning that it still is not being run in any pipelines. It is also not searchable within the testcases because it is not being run.

This MR is to add add_design_add_annotation_spec back to the suite, and also to fix any specs that have since broken.

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