Update diffy rubygem 3.1 -> 3.3

What does this MR do?

Previously opened at !25763 (comment 293021575)

Update diffy rubygem from 3.1 to 3.3

Changes: https://github.com/samg/diffy/compare/3.1.0...3.3.0

Does this MR meet the acceptance criteria?

Conformity

• Code review guidelines
• Merge request performance guidelines
• Style guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done