Docs: Change reference to v2 PassportJS docs to utilize new custom strategies docs. (#6961)

## Description

<!-- Please include a summary of the pull request and any related issues
it fixes. Please also include relevant motivation and context. -->

The v3 documentation mislead people by using PassportJS even though it's
not in v3 and custom strategies should be used instead with the correct
link.

- [x] I have read and understand the
[CONTRIBUTING.md](https://github.com/payloadcms/payload/blob/main/CONTRIBUTING.md)
document in this repository.

## Type of change

<!-- Please delete options that are not relevant. -->

- [x] Chore (non-breaking change which does not add functionality)
- [x] This change requires a documentation update

## Checklist:
- [x] Existing test suite passes locally with my changes
- [x] I have made corresponding changes to the documentation

docs/authentication/config.mdx

@@ -23,7 +23,7 @@ To enable Authentication on a collection, define an `auth` property and set it t
 | **`forgotPassword`**       | Customize the way that the `forgotPassword` operation functions. [More](/docs/authentication/config#forgot-password)                                                                                                                |
 | **`verify`**               | Set to `true` or pass an object with verification options to require users to verify by email before they are allowed to log into your app. [More](/docs/authentication/config#email-verification)                                  |
 | **`disableLocalStrategy`** | Advanced - disable Payload's built-in local auth strategy. Only use this property if you have replaced Payload's auth mechanisms with your own.                                                                                     |
-| **`strategies`**           | Advanced - an array of PassportJS authentication strategies to extend this collection's authentication with. [More](/docs/authentication/config#strategies)                                                                         |
+| **`strategies`**           | Advanced - an array of custom authentification strategies to extend this collection's authentication with. [More](/docs/authentication/custom-strategies)                                                                         |
 
 ### Forgot Password