Deprecate project.pipeline.securityReportFindings in favor of project.pipeline.vulnerabilities
## Why are we doing this work
This issue is to deprecate the `project.pipeline.securityReportFindings` query in favor of `project.pipeline.vulnerabilities`. This will follow the [Deprecation and Removal process](https://docs.gitlab.com/ee/api/graphql/#deprecation-and-removal-process).
## Relevant links
- [Replacement query issue](#343469)
## Non-functional requirements
- [ ] Documentation: Update documentation
- [ ] Testing: Remove tests
## Implementation plan
This will follow the [Deprecation and Removal process](https://docs.gitlab.com/ee/api/graphql/#deprecation-and-removal-process).
- [ ] ~backend Mark `project.pipeline.securityReportFindings` query as deprecated in the schema
- [x] ~backend Announce removal in Deprecations section
- [ ] ~backend ~~Remove `project.pipeline.securityReportFindings` query~~ [Removal issue](https://gitlab.com/gitlab-org/gitlab/-/issues/364567)
issue