fix(client): use http 0.12.0+4 to fix a wrong content-type header on …

…multipart request on http 0.12.0+3

fixes #525.

packages/graphql/pubspec.yaml

@@ -10,7 +10,7 @@ authors:
 homepage: https://github.com/zino-app/graphql-flutter/tree/master/packages/graphql
 dependencies:
   meta: ^1.1.6
-  http: ^0.12.0+2
+  http: ^0.12.0+4
   mime: ^0.9.6+2
   path: ^1.6.2
   http_parser: ^3.1.3