Fix auth cookie documentation and remove unnecessary filter in wp_set_auth_cookie()

[himanshupathak95]

Trac ticket: https://core.trac.wordpress.org/ticket/63230

The documentation for wp_set_auth_cookie() incorrectly stated that non-"Remember me" logins expire in two days. In reality, they are session cookies (they expire on the browser's close). Additionally, the auth_cookie_expiration filter was redundantly applied for non-persistent logins.

This PR -

• Updates the docblock to clarify session cookie behavior.
• Removes the auth_cookie_expiration filter call when $remember is false, as the browser ignores the filtered expiration time in this case.

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[dilipbheda]

@himanshupathak95 We can remove the else block and initialize the variable first. The $remember condition will override it if true.

diff --git a/src/wp-includes/pluggable.php b/src/wp-includes/pluggable.php
index e7ce2edb41..56b117636d 100644
--- a/src/wp-includes/pluggable.php
+++ b/src/wp-includes/pluggable.php
@@ -984,6 +984,9 @@ if ( ! function_exists( 'wp_set_auth_cookie' ) ) :
 	 * @param string      $token    Optional. User's session token to use for this cookie.
 	 */
 	function wp_set_auth_cookie( $user_id, $remember = false, $secure = '', $token = '' ) {
+		$expire     = 0;
+		$expiration = time() + ( 2 * DAY_IN_SECONDS );
+
 		if ( $remember ) {
 			/**
 			 * Filters the duration of the authentication cookie expiration period.
@@ -1001,10 +1004,6 @@ if ( ! function_exists( 'wp_set_auth_cookie' ) ) :
 			 * Needed for the login grace period in wp_validate_auth_cookie().
 			 */
 			$expire = $expiration + ( 12 * HOUR_IN_SECONDS );
-		} else {
-			/** This filter is documented in wp-includes/pluggable.php */
-			$expiration = time() + apply_filters( 'auth_cookie_expiration', 2 * DAY_IN_SECONDS, $user_id, $remember );
-			$expire     = 0;
 		}
 
 		if ( '' === $secure ) {