gql_example_http_auth_link: bump http version

Author: micimize

Diff for: examples/gql_example_http_auth_link/pubspec.yaml

@@ -8,7 +8,7 @@ dependencies:
   gql_error_link: ^0.1.0
   gql_transform_link: ^0.1.5
   gql_http_link: ^0.3.2
-  http: ^0.12.0+2
+  http: ^0.13.0
 dev_dependencies: 
   gql_pedantic: ^1.0.2
   gql_build: ^0.1.3