Test with PySpark 3.2

[ueshin]

Adds test matrix to test with PySpark 3.2.
Also upgrades PySpark 3.1 to 3.1.2.

[codecov-commenter]

Codecov Report

Merging #2203 (b64c3cc) into master (f44c050) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2203      +/-   ##
==========================================
- Coverage   94.60%   94.60%   -0.01%     
==========================================
  Files          60       60              
  Lines       13746    13746              
==========================================
- Hits        13005    13004       -1     
- Misses        741      742       +1     

Impacted Files	Coverage Δ
databricks/koalas/groupby.py	94.10% <ø> (ø)
databricks/koalas/indexes/base.py	96.79% <ø> (-0.38%)	⬇️
databricks/koalas/__init__.py	86.58% <0.00%> (+1.21%)	⬆️

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[ueshin]

I'd just merge this. Thanks.