Raise error when inputs and mask don't have same shape in Softmax

[SuryanarayanaY]

Currently keras.layers.Softmax not having check to verify inputs and mask shape same or not. As per documnetation the mask should be A boolean mask of the same shape as inputs.

But Its generating output even though mask shape is not same as that of inputs.

Hence proposing a check to raise exception when inputs and mask don't have same shape.

Fixes #19722 .

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 56.30%. Comparing base (a05ac12) to head (55d34df). Report is 195 commits behind head on master.

Files	Patch %	Lines
keras/src/layers/activations/softmax.py	0.00%	1 Missing and 1 partial :warning:

:exclamation: There is a different number of reports uploaded between BASE (a05ac12) and HEAD (55d34df). Click for more details.

HEAD has 6 uploads less than BASE

Flag	BASE (a05ac12)	HEAD (55d34df)
keras	4	1
keras-torch	1	0
keras-tensorflow	1	0
keras-jax	1	0

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #19736       +/-   ##
===========================================
- Coverage   78.53%   56.30%   -22.24%     
===========================================
  Files         498      498               
  Lines       45753    45755        +2     
  Branches     8455     8456        +1     
===========================================
- Hits        35933    25762    -10171     
- Misses       8086    18402    +10316     
+ Partials     1734     1591      -143     

Flag	Coverage Δ
keras	56.30% <0.00%> (-22.09%)	:arrow_down:
keras-jax	?
keras-numpy	56.30% <0.00%> (-0.01%)	:arrow_down:
keras-tensorflow	?
keras-torch	?

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