chore: clean up leftovers of @readonly and @writeonly directives

[Andy2003]

Description

after #3857 there was some code left, which is removed by this PR

Checklist

The following requirements should have been met (depending on the changes in the branch):

• Documentation has been updated
• TCK tests have been updated
• Integration tests have been updated
• Example applications have been updated
• New files have copyright header
• CLA (https://neo4j.com/developer/cla/) has been signed

[changeset-bot]

⚠️ No Changeset found

Latest commit: 4fa1780

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

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[neo4j-team-graphql]

Thanks for the Neo4j GraphQL Toolbox updates.

The Neo4j GraphQL Toolbox has now been torn down - reopening this PR will republish it.

[darrellwarde]

Looks great, thanks for these cleanups!