Fix DeprecatedEdxPlatformImportWarning due to EDXAPP_THIRD_PARTY_AUTH_BACKENDS default configuration
Fix DeprecatedEdxPlatformImportWarning due to EDXAPP_THIRD_PARTY_AUTH_BACKENDS default configuration

arbrandes/edx-configuration,edx/configuration,mitodl/configuration,mitodl/configuration,EDUlib/configuration,arbrandes/edx-configuration,EDUlib/configuration,edx/configuration,stvstnfrd/configuration,arbrandes/edx-configuration,stvstnfrd/configuration,EDUlib/configuration,stvstnfrd/configuration,stvstnfrd/configuration,EDUlib/configuration,arbrandes/edx-configuration,edx/configuration,EDUlib/configuration,mitodl/configuration,arbrandes/edx-configuration,edx/configuration,stvstnfrd/configuration,mitodl/configuration