Removed option to disable passive reproduction

[La-ryssa]

Brief Description of What This PR Does

Removed mentions/variables of passive reproduction in new game and difficulty classes, made it so PassiveGainOfReproductionCompounds is true by default, removed passive reproduction button from custom difficulty/advanced new game menu. Fix for #5964

Related Issues

closes #5964

Progress Checklist

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• PR author has checked that this PR works as intended and doesn't
  break existing features:
  https://wiki.revolutionarygamesstudio.com/wiki/Testing_Checklist
  (this is important as to not waste the time of Thrive team
  members reviewing this PR)
• Initial code review passed (this and further items should not be checked by the PR author)
• Functionality is confirmed working by another person (see above checklist link)
• Final code review is passed and code conforms to the
  styleguide.

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[hhyyrylainen]

I have one slight remark on these changes not going as far as I think they should in removing the feature.

[hhyyrylainen]

Can I ask why this was closed? This was very close to being completed.

[La-ryssa]

I was trying to rename my branches but doing so closed the PR's automatically... won't happen again, apologies.

[hhyyrylainen]

Thanks for clarifying. I commented as I was slightly worried that it was either a mistake or what I've also seen is that some people think they need to recreate their PRs to fix something instead of doing a force push.

[hhyyrylainen]

I think the code change is now completely correct. I'll help with the merge conflict to get this merged for today's BOTD.