Bug: react-hooks/exhaustive-deps false postive when given undefined as deps

<!-- Please provide a clear and concise description of what the bug is. Include screenshots if needed. Please test using the latest version of the relevant React packages to make sure your issue has not already been fixed. --> There's currently a false positive for the `react-hooks/exhaustive-deps` rule as it does not accept `undefined` as dependency. ```typescript // Below gives => React Hook useMemo has a missing dependency: 'byId'. Either include it or remove the dependency array. const allIds = useMemo(() => Object.keys(byId), undefined) ``` This is clearly noticeable together with TypeScript as it does not allow omitting the second `deps` parameter, with the following typings: ```typescript // allow undefined, but don't make it optional as that is very likely a mistake function useMemo<T>(factory: () => T, deps: DependencyList | undefined): T; ``` Note here that `deps` must be either a `DependencyList` or `undefined`. It is not listed as optional. React version: 17.0.1 ## Steps To Reproduce 1. Install `"eslint-plugin-react-hooks": "^4.1.0"` and extend it with `'plugin:react-hooks/recommended'` 2. Write a hook that required a dependency list, input `undefined`. ## The current behavior Gives false positive when given `undefined` for `deps`. ## The expected behavior Should allow `deps` to be set to undefined.