Update documentation of gradle support in dependency scanning

What does this MR do?

This MR documents the addition of gradle support for dependency scanning.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• [-] Code review guidelines
• [-] Merge request performance guidelines
• [-] Style guides
• [-] Database guides
• [-] Separation of EE specific content

Closes #13075 (closed)