When setting a default placeholder and an attributedString before `_textKitComponents.textView` was created, the placeholder and the string were both appearing in the text node.
`_updateDisplayingPlaceholder` is called in `setAttributedString`, but since `_textKitComponents.textView` is nil the placeholder was not hidden. Calling `_updateDisplayingPlaceholder` after `_textKitComponents.textView` loads fixes this.
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