MAINT prepare new release

[mfeurer]

This PR updates the changelog and bounces the version number. Ideally, we merge #853 before doing a new release.

[PGijsbers]

I'll finish #851 today so we can merge that too.

[codecov-io]

Codecov Report

Merging #855 into develop will decrease coverage by 0.09%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           develop    #855     +/-   ##
=========================================
- Coverage    88.49%   88.4%   -0.1%     
=========================================
  Files           37      37             
  Lines         4269    4269             
=========================================
- Hits          3778    3774      -4     
- Misses         491     495      +4

Impacted Files	Coverage Δ
openml/__version__.py	100% <100%> (ø)	⬆️
openml/datasets/functions.py	94.06% <0%> (-1.25%)	⬇️
openml/flows/functions.py	86.85% <0%> (-0.58%)	⬇️
openml/runs/functions.py	82.59% <0%> (+0.27%)	⬆️

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