Wrong substitution for Cyrillic io + combining mark

[frankrolf]

As mentioned by @codepointless here: https://github.com/adobe-fonts/source-serif/issues/72#issuecomment-768195125

io + combining mark results in wrong base glyph. The problem is a bug in the ccmp feature – these are the lines responsible:

https://github.com/adobe-fonts/source-serif/blob/main/Roman/familyGSUB.fea#L474 https://github.com/adobe-fonts/source-serif/blob/main/Italic/familyGSUB.fea#L457

[frankrolf]

Leaving this open until new fonts exist.

[frankrolf]

Fixed in 4.005: https://github.com/adobe-fonts/source-serif/releases/tag/4.005R