[Bug go/90669] go/gofrontend/types.cc:2805 contains range-based ‘for’ loops which are not C++98

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90669

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
shabits.assign(digest.begin(), digest.end()) would've worked too, and not
required any vector reallocations as it grows.