Fix language code mismatch during language switching (#1416)

## Description:
fixes #1413 
https://github.com/openfrontio/OpenFrontIO/issues/1413
## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced
- [x] I understand that submitting code with bugs that could have been
caught through manual testing blocks releases and new features for all
contributors

resources/lang/pt_BR.json

@@ -167,7 +167,7 @@
     "en": "Brazilian Portuguese",
     "native": "Português brasileiro",
     "svg": "br",
-    "lang_code": "pt_br"
+    "lang_code": "pt_BR"
   },
   "game_mode": {
     "ffa": "Free for All",

resources/lang/sv_SE.json

@@ -3,7 +3,7 @@
     "en": "Swedish",
     "native": "Svenska",
     "svg": "se",
-    "lang_code": "sv"
+    "lang_code": "sv_SE"
   },
   "common": {
     "close": "Stäng"

resources/lang/zh_CN.json

@@ -3,7 +3,7 @@
     "en": "Chinese Simplified",
     "native": "简体中文",
     "svg": "cn",
-    "lang_code": "zh"
+    "lang_code": "zh_CN"
   },
   "common": {
     "close": "关闭"

src/client/LangSelector.ts

@@ -20,14 +20,14 @@ import ja from "../../resources/lang/ja.json";
 import ko from "../../resources/lang/ko.json";
 import nl from "../../resources/lang/nl.json";
 import pl from "../../resources/lang/pl.json";
-import pt_br from "../../resources/lang/pt_br.json";
+import pt_br from "../../resources/lang/pt_BR.json";
 import ru from "../../resources/lang/ru.json";
 import sh from "../../resources/lang/sh.json";
-import sv_se from "../../resources/lang/sv_se.json";
+import sv_se from "../../resources/lang/sv_SE.json";
 import tp from "../../resources/lang/tp.json";
 import tr from "../../resources/lang/tr.json";
 import uk from "../../resources/lang/uk.json";
-import zh_cn from "../../resources/lang/zh_cn.json";
+import zh_cn from "../../resources/lang/zh_CN.json";
 
 @customElement("lang-selector")
 export class LangSelector extends LitElement {