Bump graphql from 2.5.24 to 2.6.0

Bumps [graphql](https://github.com/rmosolgo/graphql-ruby) from 2.5.24 to 2.6.0.
- [Release notes](https://github.com/rmosolgo/graphql-ruby/releases)
- [Changelog](https://github.com/rmosolgo/graphql-ruby/blob/master/CHANGELOG.md)
- [Commits](rmosolgo/graphql-ruby@v2.5.24...v2.6.0)

---
updated-dependencies:
- dependency-name: graphql
  dependency-version: 2.6.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Gemfile.lock

@@ -218,7 +218,7 @@ GEM
       thor (>= 1.0.0)
     graphiql-rails (1.10.5)
       railties
-    graphql (2.5.24)
+    graphql (2.6.0)
       base64
       fiber-storage
       logger