doc(data/int/gcd): attribution + module doc (#2217)
doc(data/int/gcd): attribution + module doc (#2217)

* doc(data/int/gcd): attribution + module doc

* reword

Co-authored-by: mergify[bot] <b09a6ee808b67e98a221404e7aaa52e0398a4954@users.noreply.github.com>
leanprover-community/mathlib,leanprover-community/mathlib