Use true instead of symbol in HAML

What does this MR do?

Uses true instance instead of a symbol in HAML.

FOSS part and enablement of its cop: !59075 (merged)

Part of #23855

Screenshots (strongly suggested)

n/a

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have not included a changelog entry because ~"technical debt" in static code analysis.
• Code review guidelines
• Style guides
• Separation of EE specific content