Legacy lists: remove pagination query parameters from `GetRecipientsAsync`

[Jericho]

You can't set page size and page number query parameters.
The endpoint shows the last 50 contacts added to the list.
To get all contacts in one list or overall, use the /v3/contactdb/exports endpoints.

This new feature will be rolled out by SendGrid between May 12 and June 30, 2025 according to email received on March 10 2025.

This new feature is documented here: https://www.twilio.com/docs/sendgrid/ui/sending-email/update-to-legacy-api-2025q1#updates-to-the-lists-resources

In fact, we should probably rename this method to GetFirst50RecipientsAsync to make it clear that the API will return no more than 50 records.

[Jericho]

The current paging feature appears to be buggy. In the following example I am requesting one record and the API returns two:

[Jericho]

The page where this new feature was documented (which I linked in my original comment) no longer exist.