Standardize curl examples in doc/api/job_artifacts.md
fixes the part of issue #509818
This MR standardizes the curl command examples in the Job Artifacts API documentation to follow the updated GitLab documentation guidelines.
Changes:
- Added
--request GETto all retrieval examples for explicit and consistent method declaration. - Standardized download examples to place
--urlbefore other parameters like--output. - Refactored single-line commands into multi-line format for improved readability.
- Ensured consistent 2-space indentation for continuation lines.
- Updated
yamlscript blocks to follow the same formatting standards. - Removed trailing backslashes from the final lines of all examples.
These changes help reduce horizontal scrolling and align this page with the project's premium documentation standards.