Update warning rel. with index_exact_words about manticoresearch

[tomatolog]

not quite sure why warning is wrong? And what case should have new warning or warning removal.

there is no point index exact source words if no morphology \ stemmer \ lemmatizer or wordforms used. The only doubt is to ignore expand_keywords option and still generate warning in this case.

[sanikolaev]

The warning is no morphology, index_exact_words=1 has no effect, ignoring, but it disappears when I add expand_keywords='1', i.e. it's still "no morphology", but there's no warning which looks wrong. There should be not just "no morphology", but "no morphology or expand_keywords" or smth which is common between them which controls this behaviour.