$ yum install -y plesk-php73-devel gcc libssh2-devel
$ yum -y install php-devel
$ wget https://pecl.php.net/get/ssh2
$ mv ssh2 ssh2-1.2.tgz

$ /opt/plesk/php/7.3/bin/pecl install ssh2-1.2.tgz
$ echo "extension=ssh2.so" > /opt/plesk/php/7.3/etc/php.d/ssh2.ini
$ plesk bin php_handler --reread
$ service plesk-php73-fpm restart