Remove duplicate ctrl+alt+left/right handling

These key combinations were registered as accelerator keystrokes in the
tab bar popup menu, but also handled by EditorListener, so they would
switch tabs *twice*. Removing the handling from EditorListener helps to
fix this.

References: arduino#4228

app/src/processing/app/EditorListener.java

@@ -45,15 +45,6 @@ public void keyPressed(KeyEvent event) {
  editor.selectPrevTab();
  }
 
- // Navigation..
- if ((event.getModifiers() & CTRL_ALT) == CTRL_ALT) {
- if (code == KeyEvent.VK_LEFT) {
- editor.selectPrevTab();
- } else if (code == KeyEvent.VK_RIGHT) {
- editor.selectNextTab();
- }
- }
-
 // if (event.isAltDown() && code == KeyEvent.VK_T) {
 // int line = textarea.getCaretLineNumber();
 // textarea.setActiveLineRange(line, line + 3);