Removes an annotation from the given plot.
The id of the plot from which you want to remove the annotation.annotation_id
The id of the annotation which was attached to PlotId_base via a call to Ngl.add_annotation.
This procedure removes an annotation that has been added to a plot via the Ngl.add_annotation function. This procedure takes two arguments, the first is a PlotId for the plot that had the annotation added to it, and the second is the id returned from the call to Ngl.add_annotation.