Fix incomplete env var rename in falcon.rb

PR #6531 renamed SERVICE_DIRECT_PORT to SERVICE_CONNECT_PORT in the
guard condition but missed the reference inside the endpoint block,
causing the secondary Falcon service to bind to a nil port.

Author: benilovj

falcon.rb

@@ -72,7 +72,7 @@
 
     endpoint do
       Async::HTTP::Endpoint.parse(
-        "http://0.0.0.0:#{ENV["SERVICE_DIRECT_PORT"]}"
+        "http://0.0.0.0:#{ENV["SERVICE_CONNECT_PORT"]}"
       ).with(protocol: protocol)
     end
   end