Update apprtc example code to support macos 10.13

It currently blocks chromium to webrtc roll after https://crrev.com/c/3646050

Bug: b/232899082
Change-Id: I87e178d91037d844fc98a28491bdfe69fa3bc9b4
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/262802
Auto-Submit: Andrey Logvin <landrey@webrtc.org>
Commit-Queue: Kári Helgason <kthelgason@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
Commit-Queue: Andrey Logvin <landrey@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36918}
diff --git a/examples/objc/AppRTCMobile/mac/APPRTCAppDelegate.m b/examples/objc/AppRTCMobile/mac/APPRTCAppDelegate.m
index 7ca63ec..36a4700 100644
--- a/examples/objc/AppRTCMobile/mac/APPRTCAppDelegate.m
+++ b/examples/objc/AppRTCMobile/mac/APPRTCAppDelegate.m
@@ -30,7 +30,7 @@
                                  NSMidY(visibleRect),
                                  1320,
                                  1140);
-  NSUInteger styleMask = NSTitledWindowMask | NSClosableWindowMask;
+  NSUInteger styleMask = NSWindowStyleMaskTitled | NSWindowStyleMaskClosable;
   _window = [[NSWindow alloc] initWithContentRect:windowRect
                                         styleMask:styleMask
                                           backing:NSBackingStoreBuffered