Function remove 

pub async fn remove(key: &str) -> Result<(), Error<FlashError>>

Available on crate feature storage and non-context=stm32 only.

Deletes an item from flash.

Additional calls to get() with the same key will return None until a new one is stored again.

This is really slow!

All items in flash have to be read and deserialized to find the items with the key. This is unlikely to be cached well.