Update core package astropy to 4.3.1

[taldcroft]

Update package astropy to version 4.3.1. (Note that 4.3.0 got skipped for technical reasons).

This includes some good stuff (https://docs.astropy.org/en/v4.3.1/whatsnew/4.3.html):

• Changes in the Time and IERS leap second handling (the pesky leap second problems on GRETA should be fixed)
• Support for multidimensional and object columns in ECSV
• Support for hiding / showing columns in a Table (I really wanted this for the ER finding notebook)

Ideally put this in the next ska3-flight and ska3-matlab releases.

[javierggt]

Installing astropy required the following updates:

• astropy-4.3.1
• intel-openmp-2021.3.0
• mkl-2021.3.0
• mkl-service-2.4.0
• mkl_fft-1.3.0
• mkl_random-1.2.2
• numexpr-2.7.3
• numpy-1.20.3
• numpy-base-1.20.3
• openssl-1.1.1k
• pyerfa-2.0.0
• scikit-learn-0.24.2
• scipy-1.6.2

This is in linux, but similar changes are required in Windows and OSX

By that I mean that those packages were installed using my autonmated incremental update. I tried by hand, and astropy requires numpy[version='>=1.19.2,<2.0a0'] so I guess all the others follow.