Remove EditorTab.getUndoManager()

This method is no longer used, and relies on an Arduino-specific patch
to RSyntaxTextArea.

Author: matthijskooijman

app/src/processing/app/EditorTab.java

@@ -44,7 +44,6 @@
 import javax.swing.text.BadLocationException;
 import javax.swing.text.Element;
 import javax.swing.text.PlainDocument;
-import javax.swing.undo.UndoManager;
 import javax.swing.text.DefaultCaret;
 
 import org.fife.ui.rsyntaxtextarea.RSyntaxDocument;
@@ -548,10 +547,6 @@ void handleRedo() {
     textarea.redoLastAction();
   }
 
-  public UndoManager getUndoManager() {
-    return textarea.getUndoManager();
-  }
-  
   public String getCurrentKeyword() {
     String text = "";
     if (textarea.getSelectedText() != null)