Project cleanup, prepare for a Spark 3.5 release

[pomadchin]

This PR just updates docs and removed Spark-3.2 from the build file.

Linked #755, #770

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (8f880ee) 95.46% compared to head (dbe25a0) 95.46%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #772   +/-   ##
=======================================
  Coverage   95.46%   95.46%           
=======================================
  Files          67       67           
  Lines        1257     1257           
  Branches       42       42           
=======================================
  Hits         1200     1200           
  Misses         57       57           

Flag	Coverage Δ
2.12-root-spark32	?
2.12-root-spark33	95.46% <ø> (ø)
2.12-root-spark34	95.46% <ø> (ø)
2.12-root-spark35	95.46% <ø> (?)
2.13-root-spark34	?
2.13-root-spark35	96.06% <ø> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.