AO3-7240 i18n rating, warning, fandom help files

[slavalamp]

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• Have you added tests for any changed functionality?
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Issue

https://otwarchive.atlassian.net/browse/AO3-7240

Purpose

i18n for rating help, warning help and fandom help files

(Also removed colons from subheaders in warning help for consistency with how nearly all other help files are formatted, the only other one that has colons there is work search numerical help)

Credit

slavalamp