wp_send_user_request() incorrect type for $request_id in phpdoc

[skithund]

$request_id param in wp_send_user_request( $request_id ) is "ID of the request created via wp_create_user_request()."

wp_create_user_request() returns int, so phpdoc type should be should be int and not string.

$request_id is "ID of the request created via wp_create_user_request()."

wp_create_user_request() returns int, so correct type for phpdoc type should be should be int.

Trac ticket: https://core.trac.wordpress.org/ticket/63682

[SergeyBiryukov]

In 60489:

Docs: Correct the type of the $request_id parameter in privacy functions.

This applies to wp_send_user_request() and wp_validate_user_request_key().

Follow-up to [43008].

Props skithund, dhruvang21, SergeyBiryukov.
Fixes #63682.