Incompatible with connection_pool 3.x

[james-caresnap]

connection_pool 3.0 changed all their positional arguments to keyword arguments, which breaks this call site:
https://github.com/reactjs/react-rails/blob/main/lib/react/server_rendering.rb#L19

connection_pool changelog:
https://github.com/mperham/connection_pool/blob/main/Changes.md#300

[G-Rath]

This is a duplicate of #1366