Removing sensitive properties from ProjectType

defaultBranch and ciConfigPath should only be available to users with
the :download_code permission for the Project, as the respository might
be private.

When implementing the authorize check on these properties, it was
found that our current Graphql::Authorize::Instrumentation class does
not work with fields that resolve to subclasses of
GraphQL::Schema::Scalar, like GraphQL::STRING_TYPE.

After discussion with other Create Team members, it has been decided
that because the GraphQL API is not GA, to remove these properties from
ProjectType, and instead implement them as part of epic
https://gitlab.com/groups/gitlab-org/-/epics/711

Issue:
https://gitlab.com/gitlab-org/gitlab-ce/issues/55316

app/graphql/types/project_type.rb

@@ -16,7 +16,6 @@ module Types
 
     field :description, GraphQL::STRING_TYPE, null: true
 
-    field :default_branch, GraphQL::STRING_TYPE, null: true
     field :tag_list, GraphQL::STRING_TYPE, null: true
 
     field :ssh_url_to_repo, GraphQL::STRING_TYPE, null: true
@@ -59,7 +58,6 @@ module Types
     end
 
     field :import_status, GraphQL::STRING_TYPE, null: true
-    field :ci_config_path, GraphQL::STRING_TYPE, null: true
 
     field :only_allow_merge_if_pipeline_succeeds, GraphQL::BOOLEAN_TYPE, null: true
     field :request_access_enabled, GraphQL::BOOLEAN_TYPE, null: true