Binder example: Need to update stack, search.fit() broken

[P. L. Lim]

Nice Binder example notebook to allow someone to explore the package without installation. 👏

However, when I ran it, I noticed a couple of things:

1. The software stack is quite old (Python 3.7, astropy 4.3.1). The current astropy LTS is in the 5.0.x series, so 4.x is no longer supported.
2. When I uncomment result = search.fit(model=model, analysis=analysis) cell in your notebook and ran it, I got a AttributeError: 'ModelInstance' object has no attribute 'galaxies'. If it is not meant to work, maybe remove it from the example? If it is supposed to work, then it needs to be fixed.
3. Some static images are not rendered but I am not sure if they are expected to or not in a Binder instance.

p.s. If you think this issue is better off moved to https://github.com/Jammy2211/autogalaxy_workspace/issues , feel free to do so. Thanks!

astropy/astropy.github.com#491 (comment)

[James Nightingale]

Bug now fixed and binder now runs on Python3.8.