Make PseudoTerminal implement NSWindowDelegate

Fixes a warning when assigning PseudoTerminal as the delegate for [self
window]; inside

(id)initWithSmartLayout:(BOOL)smartLayout windowType:(int)windowType screen:(int)screenNumber

Headers/iTerm/PseudoTerminal.h

@@ -66,7 +66,7 @@ typedef enum {
 // This class is 1:1 with windows. It controls the tabs, bottombar, toolbar,
 // fullscreen, and coordinates resizing of sessions (either session-initiated
 // or window-initiated).
-@interface PseudoTerminal : NSWindowController <PTYTabViewDelegateProtocol, PTYWindowDelegateProtocol, WindowControllerInterface>
+@interface PseudoTerminal : NSWindowController <PTYTabViewDelegateProtocol, PTYWindowDelegateProtocol, WindowControllerInterface, NSWindowDelegate>
 {
     NSPoint preferredOrigin_;
     SolidColorView* background_;