Use property name rather than getter.

GoogleSignIn/Sources/GIDEMMErrorHandler.m

@@ -162,7 +162,7 @@ typedef enum {
 #if __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_15_0
     if (@available(iOS 13, *)) {
       for (UIWindow *window in UIApplication.sharedApplication.windows) {
-        if (window.isKeyWindow) {
+        if (window.keyWindow) {
           return window;
         }
       }

GoogleSignIn/Tests/Unit/GIDEMMErrorHandlerTest.m

@@ -488,7 +488,7 @@ NS_ASSUME_NONNULL_BEGIN
                        selector:@selector(keyWindow)
                 isClassSelector:NO];
   UIWindow *mockKeyWindow = OCMClassMock([UIWindow class]);
-  OCMStub(mockKeyWindow.isKeyWindow).andReturn(YES);
+  OCMStub(mockKeyWindow.keyWindow).andReturn(YES);
   UIApplication *mockApplication = OCMClassMock([UIApplication class]);
   [GULSwizzler swizzleClass:[UIApplication class]
                    selector:@selector(sharedApplication)