Hide single option boolean flags in "help" when the default is False

[cAtaman]

Hides the default value in help texts for single option boolean flags when the default is False

• fixes Consider not showing the default value of boolean flags without a secondary option (False) #1971

Checklist:

• Add tests that demonstrate the correct behavior of the change. Tests should fail without the change.
• Add or update relevant docs, in the docs folder and in code.
• Add an entry in CHANGES.rst summarizing the change and linking to the issue.
• Add .. versionchanged:: entries in any relevant code docs.
• Run pre-commit hooks and fix any issues.
• Run pytest and tox, no tests failed.