backups - make sure to use "utf8" as encoding and not "utf-8"

src/vs/workbench/services/backup/common/backup.ts

@@ -13,8 +13,8 @@ import { ITextBufferFactory } from 'vs/editor/common/model';
 
 export const IBackupFileService = createDecorator<IBackupFileService>('backupFileService');
 
-export const BACKUP_FILE_RESOLVE_OPTIONS: IResolveContentOptions = { acceptTextOnly: true, encoding: 'utf-8' };
-export const BACKUP_FILE_UPDATE_OPTIONS: IUpdateContentOptions = { encoding: 'utf-8' };
+export const BACKUP_FILE_RESOLVE_OPTIONS: IResolveContentOptions = { acceptTextOnly: true, encoding: 'utf8' };
+export const BACKUP_FILE_UPDATE_OPTIONS: IUpdateContentOptions = { encoding: 'utf8' };
 
 /**
  * A service that handles any I/O and state associated with the backup system.