fix: add missing flex reset in XY Grid responsive vertical cell widths
fix: add missing flex reset in XY Grid responsive vertical cell widths

Apply #10891 with optimizations introduced by 7e34dc3b5 to vertical cells.

See https://github.com/zurb/foundation-sites/issues/10891

zurb/foundation-sites,zurb/foundation,colin-marshall/foundation-sites,abdullahsalem/foundation-sites,denisahac/foundation-sites,zurb/foundation,colin-marshall/foundation-sites,zurb/foundation,denisahac/foundation-sites,abdullahsalem/foundation-sites,colin-marshall/foundation-sites,DaSchTour/foundation-sites,DaSchTour/foundation-sites,zurb/foundation-sites,abdullahsalem/foundation-sites,denisahac/foundation-sites,zurb/foundation-sites