public override void DismissLine(Action onDismissalComplete)
This method is called when all Dialogue Views attached to a Dialogue Runner report that they have finished presenting this line. When this occurs, the Dialogue Runner calls DismissLine(Action) on all Dialogue Views to tell them to clear their current line from display.
Depending on how the Dialogue View presents lines, "dismissing" a line may mean different things. For example, a Dialogue View that presents on-screen text might fade the text away, or a Dialogue View that presents voice-over dialogue may not need to do anything at all (because audio finished playing when the line finished presenting.)
When the line has finished dismissing, this method calls onDismissalComplete to indicate that the dismissal is complete. When all Dialogue Views on a Dialogue Runner have finished dismissing, the Dialogue Runner moves on to the next piece of content.