Change branch name from master to main in some documents' links (#25126)

As title. And needs to backport to 1.19

docs/content/doc/contributing/localization.en-us.md

@@ -20,7 +20,7 @@ menu:
 Gitea's localization happens through our [Crowdin project](https://crowdin.com/project/gitea).
 
 For changes to an **English** translation, a pull request can be made that changes the appropriate key in
-the [english locale](https://github.com/go-gitea/gitea/blob/master/options/locale/locale_en-US.ini).
+the [english locale](https://github.com/go-gitea/gitea/blob/main/options/locale/locale_en-US.ini).
 
 For changes to a **non-English** translation, refer to the Crowdin project above.
 

docs/content/doc/contributing/localization.zh-cn.md

@@ -19,7 +19,7 @@ menu:
 
 Gitea的本地化是通过我们的[Crowdin项目](https://crowdin.com/project/gitea)进行的。
 
-对于对**英语翻译**的更改，可以发出pull-request，来更改[英语语言环境](https://github.com/go-gitea/gitea/blob/master/options/locale/locale_en-US.ini)中合适的关键字。
+对于对**英语翻译**的更改，可以发出pull-request，来更改[英语语言环境](https://github.com/go-gitea/gitea/blob/main/options/locale/locale_en-US.ini)中合适的关键字。
 
 有关对**非英语**翻译的更改，请参阅上面的 Crowdin 项目。
 

docs/content/doc/contributing/localization.zh-tw.md

@@ -19,7 +19,7 @@ menu:
 
 我們在 [Crowdin 專案](https://crowdin.com/project/gitea)上進行在地化工作。
 
-**英語系**的翻譯，可在修改[英文語言檔](https://github.com/go-gitea/gitea/blob/master/options/locale/locale_en-US.ini)後提出合併請求。
+**英語系**的翻譯，可在修改[英文語言檔](https://github.com/go-gitea/gitea/blob/main/options/locale/locale_en-US.ini)後提出合併請求。
 
 **非英語系**的翻譯，請前往上述的 Crowdin 專案。