gh-132320: random._randbelow fix

[dg-pb]

PYEXE1='main/python.exe'
PYEXE2='new/python.exe'

$PYEXE1 -m timeit -s 'from random import randint' 'randint(0, 2 - 1)'    # 298 nsec
$PYEXE2 -m timeit -s 'from random import randint' 'randint(0, 2 - 1)'    # 218 nsec

$PYEXE1 -m timeit -s 'from random import randint' 'randint(0, 2**32 - 1)'    # 519 nsec
$PYEXE2 -m timeit -s 'from random import randint' 'randint(0, 2**32 - 1)'    # 357 nsec

$PYEXE1 -m timeit -s 'from random import randint' 'randint(0, 2**128 - 1)'    # 819 nsec
$PYEXE2 -m timeit -s 'from random import randint' 'randint(0, 2**128 - 1)'    # 670 nsec

• Issue: random._randbelow soft fix with performance gain #132320

[eendebakpt]

A similar change was rejected before: see #117388.

[dg-pb]

A similar change was rejected before: see #117388.

Thanks, my bad.