Update example code in hard_sigmoid file

[keerthanakadiri]

Example code has been added in hard_sigmoid .

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.10%. Comparing base (b5ddf32) to head (5461957).

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #20515   +/-   ##
=======================================
  Coverage   82.10%   82.10%           
=======================================
  Files         515      515           
  Lines       47765    47765           
  Branches     7480     7480           
=======================================
  Hits        39219    39219           
  Misses       6734     6734           
  Partials     1812     1812           

Flag	Coverage Δ
keras	81.95% <ø> (ø)
keras-jax	65.03% <ø> (ø)
keras-numpy	60.02% <ø> (ø)
keras-tensorflow	66.02% <ø> (ø)
keras-torch	64.96% <ø> (ø)

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