glib/date test fails

With glibc 2.29 and glib 2.58.3:

ERROR:../glib-2.58.3/glib/tests/date.c:390:test_month_names: assertion failed (buf_casefold == o_casefold): (
"16 \316\271\316\277\317\205\316\273 2018" ==
"16 \316\271\316\277\317\215\316\273 2018")

I wrapped so you can see the difference, \205 vs \215.

Paging @rluzynski as he is clearly a i18n genius.