fix locale detect error on mobile apps (#5956)

react/features/base/i18n/languageDetector.native.js

     detect() {
         const { LocaleDetector } = NativeModules;
 
-        return LocaleDetector.locale.replace(/_/, '-');
+        return LocaleDetector.locale.replace(/[_-]/, '');
     },
 
     init: Function.prototype,