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. This was
probably added in an attempt to work around the broken accelerator keys
on the tab bar popup menus, but in practice this only meant that the
shortcut would sometimes (and now that the accelerator keys are fixed,
always) switch tabs *twice*. Removing the handling from EditorListener
helps to fix this.

References: arduino#4228

app/src/processing/app/EditorListener.java

@@ -54,15 +54,6 @@ public void keyPressed(KeyEvent event) {
  sketch.handlePrevCode();
  }
 
- // Navigation..
- if ((event.getModifiers() & CTRL_ALT) == CTRL_ALT) {
- if (code == KeyEvent.VK_LEFT) {
- sketch.handlePrevCode();
- } else if (code == KeyEvent.VK_RIGHT) {
- sketch.handleNextCode();
- }
- }
-
 // if (event.isAltDown() && code == KeyEvent.VK_T) {
 // int line = textarea.getCaretLineNumber();
 // textarea.setActiveLineRange(line, line + 3);