[1888-N] corrects the Forbidden City private ability

[philcampeau]

Fixes #11400

Before clicking "Create"

• Branch is derived from the latest master
• Add the pins or archive_alpha_games label if this change will break existing games
• Code passes linter with docker compose exec rack rubocop -a
• Tests pass cleanly with docker compose exec rack rake

Implementation Notes

Explanation of Change

The Forbidden City private changed between the prototype phase and the final release. The final release version was never implemented. This implements it, but only when playing with the 1888-North variant, since the prototype version is still available for play on the site.

This will require pinning any games using the :north variant.

Screenshots

Any Assumptions / Hacks