fix: adjust graphql port in docker setup

[gruberb]

Description

The GraphQL port in the docker setup was outdated and therefore couldn't access the GraphQL playground anymore.

PR Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added or updated tests that comprehensively prove my change is effective or that my feature works

[dvdplm]

Would be good to have an integration test for this sort of thing, to avoid having to debug silly papercuts like these?