package/python-numpy: bump to version 1.16.4

See:
https://github.com/numpy/numpy/releases/tag/v1.16.4



Signed-off-by: Romain Naour <romain.naour@gmail.com>
Cc: Asaf Kahlon <asafka7@gmail.com>
Cc: Samuel Martin <s.martin49@gmail.com>
Cc: Yegor Yefremov <yegorslists@googlemail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>