package/php: bump version to 7.4.20
Changelog: https://www.php.net/ChangeLog-7.php#7.4.20
Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit f42a500e41ff294aaed3800b159d0cc4b966d999)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>