Exclude Current user email and send notification

First, you should know that current_user_can() only accepts capabilities, not roles, so you are using it wrong and you can end up with unexpected results.

That being said, to exlude users form WP_User_Query you can use the exclude parameter:

// Get current user data
$user = wp_get_current_user();

// Check if current user is a subscriber
if( ! empty( $user ) && in_array( "subscriber", (array) $user->roles ) ) {

    $user_query = new WP_User_Query( array(
                                           'role'   => 'subscriber',
                                           // exlude current user
                                           'exclude' => array( $user->ID ),
                                     )
    );

    $subscribers = $user_query->get_results();

    if( ! empty( $subscribers ) ) {
        foreach ( $subscribers as $user )  {

            $mail = $user->user_email;
            $subject  ="this is example";
            $message  = "";
            $message .= "$post_permalink\n";

            wp_mail( $mail, $subject, $message);

        }
    }

}