Pin yara-python v4.2.3

[yankovs]

In version v4.2.3 of yara-python accessing strings of a yara.Match object returns list of tuples of the form (<offset>,<identifier>,<data>) as seen in docs. However, in new v4.3.0 they've abstracted it to return List[StringMatch], where StringMatch itself also has abstracted StringMatchInstance member.

Shouldn't be too hard to refactor, but in the meantime maybe it's best to pin

[yankovs]

I literally have no idea why it chose to include changes to dnfile requirement in diff

[psrok1]

Thanks! I also think that the best we can do is to temporarily pin version.