refactor(number_theory/bernoulli_polynomials): improve names (#11805)
refactor(number_theory/bernoulli_polynomials): improve names (#11805)

Cleanup the bernoulli_polynomials file



Co-authored-by: Riccardo Brasca <0677c91f180214c5b55c65ca22f8fe16347bef31@gmail.com>

leanprover-community/mathlib,leanprover-community/mathlib