i18n: restore Malayalam and Serbian files, remove ml-IN from the language selector (go-gitea#4576)

* Closes https://codeberg.org/forgejo/forgejo/issues/4563
* A followup to my 2024-February investigation in the Localization room

* Restore Malayalam and Serbian locales that were deleted in 067b0c2 and f910924. Bulgarian was also deleted, but we already have better Bulgarian translation.
* Remove ml-IN from the language selector. It was not usable for 1.5 years, has ~18% completion and was not maintained in those ~1.5 years. It could also have placeholder bugs due to refactors.

Restoring files gives the translators a base to work with and makes the project advertised on Weblate homepage for logged in users in the Suggestions tab. Unlike Gitea, we store our current translations directly in the repo and not on a separate platform, so it makes sense to add these files back.
Removing selector entry avoids bugs and user confusion. I will make a followup for the documentation.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/4576
Reviewed-by: twenty-panda <[email protected]>

Author: 0ko

modules/setting/i18n.go

@@ -34,7 +34,6 @@ var defaultI18nLangNames = []string{
 	"fa-IR", "فارسی",
 	"hu-HU", "Magyar nyelv",
 	"id-ID", "Bahasa Indonesia",
-	"ml-IN", "മലയാളം",
 }
 
 func defaultI18nLangs() (res []string) {