Upgrade GraphQL gem to 1.9.11 for EE

What does this MR do?

CE version is at https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/31980

We were originally using graphql (1.8.1) while the graphql-ruby gem is at 1.9.11. Two other MRs upgraded to 1.8.4 and 1.8.17. This brings us up all the way to 1.9.11

Doing so allows us to gain bug fixes, new functionality and optimization benefits, such as Lookahead:

GraphQL-Ruby 1.9+ includes GraphQL::Execution::Lookahead for checking whether child fields are selected. You can use this to optimize database access, for example, selecting only the needed fields from the database.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Performance and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers