Remove duplicate finding link creation

What does this MR do?

This MR prevents the StoreReportService from creating duplicate finding links as part of the work for #330882 (closed).

Screenshots or Screencasts (strongly suggested)

N/A

How to setup and validate locally (strongly suggested)

1. Enable the vulnerability_finding_replace_metadata flag

   Feature.enable(:vulnerability_finding_replace_metadata)

2. On the master branch, run a pipeline with a dependency scan twice (https://gitlab.com/gitlab-examples/security/security-reports)
3. Go to a Dependency Scanning vulnerability. There should be 2 of each link.
4. On this MR branch, run the pipeline again.
5. Go back to the Dependency Scanning vulnerability. There should still only be 2 of each link.

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Related to #330882 (closed)