Improve backport-locales.go (#23807)

Improve backport-locales.go (#23807)

ps: there are more broken translation strings in 1.20 (main), most of
them are still caused by incorrect quoting/unquoting. For example,
translators might write text ``` `my text ```, such incorrect encoding
might break crowdin & Gitea's locale package.

In the future, a Go `update-locales.go` should replace the legacy
`update-locales.sh`.