[BUG] Vista Image subtraction doesn't actually work

[robertdstein]

Describe the bug
Firstly #864 needs to be fixed.

Then, there is a problem that vista images are too large, which can be fixed by tweaking the swarp config here:

mirar/mirar/pipelines/winter/config/files/config.swarp

Line 75 in 9ac5a07

#------------------------------ Memory management -----------------------------

Tweaking this allows image subtraction to take place. However, even after that, the subtraction itself fails spectacularly. in some cases.

This is leading to a bunch of spurious detections.

I propose to do three things:

• fix the swarp config
• fix the astroquery issue upstream via PR
• completely disable subtractions with VISTA until we are confident that it is doing the right thing most of the time.