Remove the 3rd party auth vars.

3rd Party auth is now managed via django admin an not from json config.

https://github.com/edx/edx-platform/pull/8140/files#diff-8a23909bc8d201fba8525b1dd6396247

playbooks/roles/edxapp/defaults/main.yml

@@ -120,7 +120,6 @@ EDXAPP_CAS_ATTRIBUTE_PACKAGE: ""
 EDXAPP_ENABLE_AUTO_AUTH: false
 # Settings for enabling and configuring third party authorization
 EDXAPP_ENABLE_THIRD_PARTY_AUTH: false
-EDXAPP_THIRD_PARTY_AUTH: {}
 
 EDXAPP_ENABLE_EDXNOTES: false
 
@@ -660,7 +659,6 @@ edxapp_generic_auth_config:  &edxapp_generic_auth
   CELERY_BROKER_USER: "{{ EDXAPP_CELERY_USER }}"
   CELERY_BROKER_PASSWORD: "{{ EDXAPP_CELERY_PASSWORD }}"
   GOOGLE_ANALYTICS_ACCOUNT: "{{ EDXAPP_GOOGLE_ANALYTICS_ACCOUNT }}"
-  THIRD_PARTY_AUTH: "{{ EDXAPP_THIRD_PARTY_AUTH }}"
   AWS_STORAGE_BUCKET_NAME: "{{ EDXAPP_AWS_STORAGE_BUCKET_NAME }}"
   DJFS: "{{ EDXAPP_DJFS }}"
   CREDIT_PROVIDER_SECRET_KEYS: "{{ EDXAPP_CREDIT_PROVIDER_SECRET_KEYS }}"