Update pubspec.yaml

Author: hungryemon

pubspec.yaml

@@ -18,7 +18,7 @@ dependencies:
   lints: ^3.0.0
   characters: ^1.3.0
   diff_match_patch: ^0.4.1
-  i18n_extension: ^10.0.1
+  i18n_extension: ^12.0.1
   device_info_plus: ^9.1.1
   platform: ^3.1.3
   pasteboard: ^0.2.0