Adopt GraphQL Java 26.1 baseline

[bclozel]

See https://github.com/graphql-java/graphql-java/releases/tag/v26.0 and https://github.com/graphql-java/graphql-java/releases/tag/v26.1

[bclozel]

Blocked on graphql-java/graphql-java#4436

[bclozel]

The blocking issue has been solved, we'll upgrade to the next available release.