compilation errors with `3.0.0-RC6` with `gql`

[yanns]

The version 3.0.0-RC6 cannot compile when using qgl:

: method parboiledToSourceMapper in object ParserConfig cannot be accessed as a member of object sangria.parser.ParserConfig from class CoreWsGraphQLHttpServiceSpec in package core
[error]     val queryProjects = gql"""
[error]                         ^

ParserConfig.parboiledToSourceMapper should be made public.

[performantdata]

#796