[MRG] switch include_lowest to True in discretizers

[solegalli]

closes #626 closes #628

See for doc fix: https://github.com/sphinx-doc/sphinx/issues/11062

In case we need to revert

[codecov[bot]]

Codecov Report

Merging #627 (256514e) into main (71efa79) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #627   +/-   ##
=======================================
  Coverage   97.88%   97.88%           
=======================================
  Files          96       96           
  Lines        3554     3554           
  Branches      685      685           
=======================================
  Hits         3479     3479           
  Misses         28       28           
  Partials       47       47           

Impacted Files	Coverage Δ
feature_engine/discretisation/base_discretiser.py	100.00% <ø> (ø)
feature_engine/discretisation/equal_width.py	100.00% <ø> (ø)

:mega: We’re building smart automated test selection to slash your CI/CD build times. Learn more