6 files declare their use of SubRequestBuffer in GraphQL 8.3

BlocksByRegion.php in modules/graphql_core/src/Plugin/GraphQL/Fields/Blocks/BlocksByRegion.php

Breadcrumbs.php in modules/graphql_core/src/Plugin/GraphQL/Fields/Breadcrumbs/Breadcrumbs.php

Context.php in modules/graphql_core/src/Plugin/GraphQL/Fields/Context/Context.php

InternalRequest.php in modules/graphql_core/src/Plugin/GraphQL/Fields/Routing/InternalUrl/InternalRequest.php

LanguageSwitchLinks.php in modules/graphql_core/src/Plugin/GraphQL/Fields/LanguageSwitch/LanguageSwitchLinks.php

RouteEntity.php in modules/graphql_core/src/Plugin/GraphQL/Fields/Routing/RouteEntity.php