Adds scikit-learn dependency to setup

[sampathweb]

#20599 added dependency to sklearn, but was not included in pyproject.toml. This caused the nightly wheel to not include it and fails TensorFlow nightly build. This PR adds scikit-learn as a Keras Deps.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.52%. Comparing base (a237437) to head (060ea3f).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #20644   +/-   ##
=======================================
  Coverage   82.52%   82.52%           
=======================================
  Files         529      529           
  Lines       49018    49018           
  Branches     7625     7625           
=======================================
  Hits        40454    40454           
  Misses       6727     6727           
  Partials     1837     1837           

Flag	Coverage Δ
keras	82.36% <ø> (ø)
keras-jax	65.68% <ø> (ø)
keras-numpy	60.57% <ø> (-0.01%)	⬇️
keras-tensorflow	66.48% <ø> (ø)
keras-torch	65.50% <ø> (ø)

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