Split relativizeSymlinks parameterized tests in separate tests

[Muskan244]

Follow-up to PR #13553 based on review by @koppor.

This PR improves the readability of the code by splitting relativizeSymlinks() parameterized test cases into separate test cases.

Steps to test

• Build JabRef and run the full test suite:
  Gradle: ./gradlew test
  Ensure all tests in FileUtilTest related to symlink handling pass without errors.

Mandatory checks

• I own the copyright of the code submitted and I license it under the MIT license
• I manually tested my changes in running JabRef (always required)
• I added JUnit tests for changes (if applicable)
• [/] I added screenshots in the PR description (if change is visible to the user)
• [/] I described the change in CHANGELOG.md in a way that is understandable for the average user (if change is visible to the user)
• [/] I checked the user documentation: Is the information available and up to date? If not, I created an issue at https://github.com/JabRef/user-documentation/issues or, even better, I submitted a pull request updating file(s) in https://github.com/JabRef/user-documentation/tree/main/en.

[trag-bot]

@trag-bot didn't find any issues in the code! ✅✨

[subhramit]

Please clean up the git history.
It has commits unrelated to the changes and by other authors.

[koppor]

Please clean up the git history.
It has commits unrelated to the changes and by other authors.

I think, its OK this time - diff is right.

Next time @Muskan244 please base on latest main.

[Muskan244]

Got it, thanks! I’ll rebase on the latest main in future PRs.

[koppor]

Got it, thanks! I’ll rebase on the latest main in future PRs.

No need for rebase:

git fetch upstream

git checkout upstream/main

git checkout -b newbranch

(There are surely more easy steps, but this is what I do)

[Muskan244]

Thanks for clarifying, I’ll use this approach from next time.