The workaround involves setting up a Text Replacement for the letter "i". To do this, go to Settings -> General -> Keyboard -> Text Replacement, and tap the plus (+) button. In the Phrase field, type an uppercase "I", and in the Shortcut field, type a lowercase "i". This should fix the problem until Apple addresses it properly in the next iOS update, which shouldn't be far off.
If you're new to AirPods, considering buying a pair, or just want to pick up some new tips.