Fix comment

[dayo09]

Let's fix comment in AveragePooling2D.

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[dayo09]

This comment is about valid padding. Let's fix this to represent same padding.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.68%. Comparing base (3d2db56) to head (116cc07).

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #21340   +/-   ##
=======================================
  Coverage   82.68%   82.68%           
=======================================
  Files         565      565           
  Lines       54825    54825           
  Branches     8515     8515           
=======================================
  Hits        45333    45333           
  Misses       7406     7406           
  Partials     2086     2086           

Flag	Coverage Δ
keras	82.49% <ø> (ø)
keras-jax	63.64% <ø> (ø)
keras-numpy	58.77% <ø> (-0.01%)	⬇️
keras-openvino	33.13% <ø> (ø)
keras-tensorflow	64.03% <ø> (ø)
keras-torch	63.67% <ø> (ø)

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[fchollet]

LGTM