Fix double line number hash on pipeline security tab

What does this MR do and why?

Related #498464

Fix double line number hash on pipeline security tab

This fixes an issue where the link to a line number in a file on the pipeline security tab can contain the hash for the line number(s) twice.

Changelog: fixed EE: true

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Before	After

How to set up and validate locally

1. Import https://gitlab.com/gitlab-examples/security/security-reports
2. Run pipeline on master
3. Go to pipeline > security tab
4. Find a finding with a file link with a line number (e.g. secrets.go:114)
5. Validate that the link contains the hash only once #L114