Language pack removal

[pkevan]

In #23 there were two language packs removed from /lang due to being a high enough coverage on https://translate.wordpress.org/projects/wp-plugins/secure-custom-fields/, but it's not clear what that percentage is. We should document what level we feel is a suitable level, and remove as necessary.

[kraftbj]

It's 90% ( https://github.com/WordPress/wordpress.org/blob/7bcd368b66c9e098bce1314a9f4af61d7ac067a1/wordpress.org/public_html/wp-content/plugins/wporg-gp-customizations/inc/cli/class-language-pack.php#L18 )

You can confirm via the #meta-language-packs channel in Slack, e.g. https://wordpress.slack.com/archives/C0E7F4RND/p1743947994603029

It'll report which translations are generating new language packs (e.g. new translations added to a pack at the threshold) or if a language is under the threshold.

See also https://translate.wordpress.org/projects/wp-plugins/secure-custom-fields/language-packs/

nl_NL_formal is almost there!