fix: map Cyrillic ѝ (i with grave) to i instead of u

[spokodev]

ѝ (U+045D, Cyrillic small letter i with grave) is a stressed variant of и — the same letter with a grave accent — used in Bulgarian and Macedonian orthography (e.g. the Bulgarian pronoun ѝ). It should transliterate to i like и, but the char map has it as u, so slugify('ѝ') → 'u'. No transliteration scheme maps this character to u.

Correct the mapping to i. The existing bg locale test had baked the wrong u into its expected output, which is updated accordingly.