Fix extra new line in ATT&CK-coverage.md

[shashank-elastic]

Pull Request

Issue link(s): PR(s) are being raised for newline with no actual changes
Example - #4211

Summary - What I changed

• Remove the additional new line, so PR is created only when content has changed
• Remove spaces from the header content so we wont have issues like in PR Update ATT&CK coverage URL(s) in docs/ATT&CK-coverage.md #4264

How To Test

• Unit Test should pass
• We have Ran a workflow from the private branch https://github.com/elastic/detection-rules/actions/runs/11742727980/job/32714051302?pr=4263
• Only Updates are seen as in this PR with no header content changes https://github.com/elastic/detection-rules/pull/4265/files

Checklist

• Added a label for the type of pr: bug, enhancement, schema, maintenance, Rule: New, Rule: Deprecation, Rule: Tuning, Hunt: New, or Hunt: Tuning so guidelines can be generated
• Added the meta:rapid-merge label if planning to merge within 24 hours
• Secret and sensitive material has been managed correctly
• Automated testing was updated or added to match the most common scenarios
• Documentation and comments were added for features that require explanation

Contributor checklist

• Have you signed the contributor license agreement?
• Have you followed the contributor guidelines?

[protectionsmachine]

Bug - Guidelines

These guidelines serve as a reminder set of considerations when addressing a bug in the code.

Documentation and Context

• Provide detailed documentation (description, screenshots, reproducing the bug, etc.) of the bug if not already documented in an issue.
• Include additional context or details about the problem.
• Ensure the fix includes necessary updates to the release documentation and versioning.

Code Standards and Practices

• Code follows established design patterns within the repo and avoids duplication.
• Code changes do not introduce new warnings or errors.
• Variables and functions are well-named and descriptive.
• Any unnecessary / commented-out code is removed.
• Ensure that the code is modular and reusable where applicable.
• Check for proper exception handling and messaging.

Testing

• New unit tests have been added to cover the bug fix or edge cases.
• Existing unit tests have been updated to reflect the changes.
• Provide evidence of testing and detecting the bug fix (e.g., test logs, screenshots).
• Validate that any rules affected by the bug are correctly updated.
• Ensure that performance is not negatively impacted by the changes.
• Verify that any release artifacts are properly generated and tested.

Additional Checks

• Ensure that the bug fix does not break existing functionality.
• Review the bug fix with a peer or team member for additional insights.
• Verify that the bug fix works across all relevant environments (e.g., different OS versions).
• Confirm that all dependencies are up-to-date and compatible with the changes.
• Confirm that the proper version label is applied to the PR patch, minor, major.

[eric-forte-elastic]

🟢 Manual review, looks good to me! 👍