Rename ko.po back to ko_KR.po.

While it was renamed from ko_KR.UTF-8.po to ko.po in #10976, @uhojin,
a Korean locale maintainer, notes [1] that “ko_KR [*South* Korean] makes
more sense in locale context just to avoid any potential confusion
between 한국어 vs 조선어”.

Despite ko_KP (North Korean) not being present in glibc (as of version
2.43), and the ISO639 maintainers expressing disapproval of ko_KP [2],
it is possible opinions may change in the future, and individual
opinions may be contested—disambiguating doesn't hurt.

[1]: https://github.com/ghostty-org/ghostty/pull/10976#discussion_r2861424171
[2]: https://github.com/ghostty-org/ghostty/pull/10976#discussion_r2861359240

CODEOWNERS

@@ -177,7 +177,7 @@
 /po/id.po @ghostty-org/id_ID
 /po/it.po @ghostty-org/it_IT
 /po/ja.po @ghostty-org/ja_JP
-/po/ko.po @ghostty-org/ko_KR
+/po/ko_KR.po @ghostty-org/ko_KR
 /po/lt.po @ghostty-org/lt_LT
 /po/lv.po @ghostty-org/lv_LV
 /po/mk.po @ghostty-org/mk_MK

src/os/i18n_locales.zig

@@ -37,7 +37,7 @@ pub const locales = [_][:0]const u8{
     "ru",
     "uk",
     "pl",
-    "ko",
+    "ko_KR",
     "mk",
     "tr",
     "id",