Remove marriage abroad code

[ellohez]

This is part of the Clean up 'Get married abroad' smart answer (post-retirement) work
The code relating to Get Married Abroad can now safely be deleted now that the Smart Answer has successfully been migrated to the new version now hosted by Mainstream Publisher.

This includes

• Flow class files (app/flows/marriage_abroad...)
• ERB templates Directory (app/flows/marriage_abroad...)
• YAML files (config/smart_answers/marriage_abroad... and config/smart_answers/rates/marriage_abroad...)
• Calculators, data queries and other (lib/smart_answer/calculators/marriage_abroad
• Tests
• Docs

[Tetrino]

LGTM!

[mtaylorgds]

Might be worth updating the docs/debugging/visualising-flows.md file to use a different example from marriage abroad, so that the example CLI commands can be copy and pasted and "just work".

[ellohez]

Might be worth updating the docs/debugging/visualising-flows.md file to use a different example from marriage abroad, so that the example CLI commands can be copy and pasted and "just work".

I have updated this so the example is now check-uk-visa and I ran the commands so should all be fine.