gh-36877: Improve code style for matrix2.pyx file

    
- Correct pycodestyle and remove check condition for columns in
prod_of_row_sums() function
- Improve code style and remove an unwanted if condition in restrict()
function
- Improve code style of matrix2.pyx file
- Improve code style for matrix2.pyx

This patch improves the code style as mentioned in the sage
documentation and removes
some unnecessary lines which were commented before and was not removed.
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None
    
URL: #36877
Reported by: Ruchit Jagodara
Reviewer(s): Kwankyu Lee