Remove configuration key for GraphQL schema path

[bclozel]

Currently, the GraphQL schema is exposed under /graphql/schema (so relative to the main graphql endpoint) and is configurable with the spring.graphql.schema.printer.path configuration property.

In theory, this could be set to any value and exposed anywhere. This is causing several issues:

• it makes the security configuration more complex if the schema is not exposed under the main graphql path
• while there's no standard for this, enforcing a consistent location for the schema will help Gateway products
• for now, we don't see a strong use case for configuring this