convert/ICU.c: add a comment how I test w/o UCONFIG_NO_TRANSLITERATION [ci skip]
convert/ICU.c: add a comment how I test w/o UCONFIG_NO_TRANSLITERATION [ci skip]

jddurand/c-tconv,jddurand/c-tconv,jddurand/c-tconv,jddurand/c-tconv