Fix Swizzling Test

• This is a *temporary* solution to a bug we've had with an old test.
• The `testSwizzling` test causes the `UNUserNotificationCenterDelegate` to get nullified on the notification center singleton.
• Since some tests use this delegate to mock a push notification delivery, this can break these tests
• Since XCTest cases are run in alphabetical order, we've been lucky that we've never noticed this in the past since `testSwizzling` was run AFTER all of our tests that use the `UNUserNotificationCenterDelegate.willPresentNotification...` method are alphabetically BEFORE the testSwizzling test

• TODO: The notification center delegate gets set to a dummy instance then nullified. We COULD fix this by simply resetting it back to the original value - but this causes issues with swizzling
• We will probably need to change the `setOneSignalUNDelegate` swizzle method to make sure it allows the UNUserNotificationCenterDelegate to be reset without messing up the swizzling which causes infinite loops, etc.

Author: Nightsd01

iOS_SDK/OneSignalSDK/UnitTests/UnitTests.m

@@ -1918,7 +1918,10 @@ - (void)testPushNotificationToken {
 }
 
 //tests to make sure that UNNotificationCenter setDelegate: duplicate calls don't double-swizzle for the same object
-- (void)testSwizzling {
+// TODO: This test causes the UNUserNotificationCenter singleton's Delegate property to get nullified
+// Unfortunately the fix is not as simple as just setting it back to the original when the test is done
+// To avoid breaking other tests, this test should be executed last, and since tests are alphabetical order, adding Z's does this.
+- (void)testZSwizzling {
     UNUserNotificationCenter *center = [UNUserNotificationCenter currentNotificationCenter];
 
     DummyNotificationCenterDelegate *delegate = [[DummyNotificationCenterDelegate alloc] init];