Revert "Create emphemeral IssueLink if Feedback is present"

What does this MR do?

This MR reverts the changes done in !38592 (merged) because it introduces a bug.

tl;dr GraphQL gem can't handle records with an id of nil which results in

GraphQL::Pagination::Connections::ImplementationMissingError: Couldn't find a connection wrapper for Vulnerabilities::IssueLink during Vulnerability.issueLinks (#<Vulnerabilities::IssueLink id: nil, vulnerability_id: 1727730, issue_id: 3448, link_type: "created", created_at: nil, updated_at: nil>)

See https://sentry.gitlab.net/gitlab/gitlabcom/issues/1740120/?query=is%3Aunresolved for more details.

We will be looking for a workaround or a database migration in order to solve https://gitlab.com/gitlab-org/gitlab/-/issues/223770

This did not fail on development environment because Labkit::Tracing is not enabled. On production we have tracing enabled and I imagine that the be the source of the issue.

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

Closes #223770