Remove translation for -help-debug options

Do not translate -help-debug options, Many technical terms, and
only a very small audience, so is unnecessary stress to translators.

Brings the code up to date with translation string policy in
doc/translation_strings_policy.md.

Also remove no-longer-relevant "In this mode -genproclimit controls how
many blocks are generated immediately." (as of #5957) from regtest help.