Fix broken QA test

What does this MR do?

This MR fixes a broken QA test.

With the feature flag :epic_new_issue enabled by default, the QA test that adds/removes issue to/from epic was broken.

This MR fixes it by:

• Adjusting the page object views and a method
• Adding a new data-qa-selector attribute in an element
• Deleting a data-qa-selector attribute that is not in use anymore.

Closes #197486 (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

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