deps: Bump json_annotation range to resolve a warning in build_runner check

Just to get the output of `tools/check build_runner` clear of
warnings, so future warnings stand out.

Discussion:
  https://chat.zulip.org/#narrow/stream/243-mobile-team/topic/build_runner.20unexpected.20output/near/1929816

Author: chrisbobbe

pubspec.yaml

@@ -51,7 +51,7 @@ dependencies:
   http: ^1.0.0
   http_parser: ^4.0.2
   image_picker: ^1.0.0
-  json_annotation: ^4.8.1
+  json_annotation: ^4.9.0
   mime: ^1.0.5
   package_info_plus: ^8.0.0
   path: ^1.8.3