The RemoveText method will remove the argument Text instance from the engine so it will no longer be drawn or have every-frame management applied. RemoveText also removes the Text from any PositionedObjectList that it is a part of (assuming a two-way relationship).
Code Example
// Assuming text is a valid Text which has been added to the TextManager
TextManager.RemoveText(text);
RemoveText can also remove entire lists:
PositionedObjectList<Text> textList = new PositionedObjectList<Text>();
// populate textList by adding Text objects to it.
// This will remove all Text objects contained in textList and also
// clear textList if it is a two-way list.
TextManager.RemoveText(textList);