Apollo Server v4 embedded Explorer does not run preflight script for introspection automatic polling.
### Issue Description

When running an operation the preflight script runs and our shared Authorization is correctly sent to our server.

However if we turn on the automatic polling, the preflight script does not run, and the Explorer is sending the wrong value for the Authorization header. Introspection fails because of the wrong header value.

This was working fine in Apollo server v3.

### Link to Reproduction

http://localhost:4444/

### Reproduction Steps

1. Set up Apollo v4 server using Express.
2. The default for the server endpoint is to show the Explorer.
3. Create a preflight script to set the value of a token: explorer.environment.set('token', 'some value')
4. Added a shared authorization header using the value of token: Authorization Token {{token}}.
5. Turn on automatic polling. The preflight script does not run and the Authorization header has the wrong value in it.