Docs don't match typescript types

[dborstelmann]

https://www.apollographql.com/docs/apollo-server/migration/#handler-is-always-async

This doc says callback can be ignored.

Expected 3 arguments, but got 2.ts(2554)
handler.d.ts(87, 5): An argument for 'callback' was not provided.
const apolloHandler: (event: any, context: Context, callback: Callback<any>) => void | Promise<any>

apollo-server-lambda 3.4

[glasser]

Duplicate of #5592. There's a discussion of a potential fix on #5593 but the submitted PR does not build.