Clean up obsolete api helpers, GraphQL queries and mutations

app/assets/javascripts/lib/utils/error_utils.js

ee/app/assets/javascripts/api.js

ee/app/assets/javascripts/api/subscriptions_api.js

...raise_leads/hand_raise_lead/init_hand_raise_lead_modal.js

ee/app/assets/javascripts/registrations/company/new/index.js

.../javascripts/subscriptions/buy_addons_shared/constants.js

...ts/javascripts/subscriptions/buy_addons_shared/graphql.js

.../subscriptions/buy_addons_shared/graphql/typedefs.graphql

ee/app/assets/javascripts/subscriptions/graphql/graphql.js

...criptions/graphql/mutations/update_state.mutation.graphql

...s/new_subscription_invoice_preview.customer.query.graphql

...ions/graphql/queries/order_preview.customer.query.graphql

...ubscriptions/graphql/queries/plans.customer.query.graphql

...scripts/subscriptions/graphql/queries/state.query.graphql

ee/app/assets/javascripts/subscriptions/graphql/resolvers.js

...assets/javascripts/subscriptions/new/formatting_mixins.js

...low/graphql/mutations/activate_next_step.mutation.graphql

...low/graphql/mutations/update_active_step.mutation.graphql

...s/purchase_flow/graphql/queries/active_step.query.graphql

...flow/graphql/queries/furthest_accessed_step.query.graphql