Use Ruby 2.7 in specs to remove Ruby 2.1/2.2/2.3

What does this MR do?

Uses Ruby 2.7 in specs to remove Ruby 2.1/2.2/2.3

Does this MR meet the acceptance criteria?

Conformity

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

Closes #195165 (closed)