Revert "Fix RCTAlertController not showing when using SceneDelegate o…

…n iOS 13.0+ (facebook#35716)"

This reverts commit 0c53420.

React/CoreModules/RCTAlertController.m

@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#import <React/RCTUtils.h>
+
+#import <React/RCTAlertController.h>
+
+@interface RCTAlertController ()
+
+@property (nonatomic, strong) UIWindow *alertWindow;
+
+@end
+
+@implementation RCTAlertController
+
+- (UIWindow *)alertWindow
+{
+  if (_alertWindow == nil) {
+    UIWindow *keyWindow = RCTSharedApplication().keyWindow;
+    if (keyWindow) {
+      _alertWindow = [[UIWindow alloc] initWithFrame:keyWindow.bounds];
+      _alertWindow.rootViewController = [UIViewController new];
+      _alertWindow.windowLevel = UIWindowLevelAlert + 1;
+    } else {
+      // keyWindow is nil, so we cannot create and initialize _alertWindow
+      NSLog(@"Unable to create alert window: keyWindow is nil");
+    }
+  }
+
+  return _alertWindow;
+}
+
+- (void)show:(BOOL)animated completion:(void (^)(void))completion
+{
+  if (@available(iOS 13.0, *)) {
+    UIUserInterfaceStyle style =
+        RCTSharedApplication().delegate.window.overrideUserInterfaceStyle ?: UIUserInterfaceStyleUnspecified;
+    self.overrideUserInterfaceStyle = style;
+  }
+  [self.alertWindow makeKeyAndVisible];
+  [self.alertWindow.rootViewController presentViewController:self animated:animated completion:completion];
+}
+
+- (void)hide
+{
+  [_alertWindow setHidden:YES];
+
+  if (@available(iOS 13, *)) {
+    _alertWindow.windowScene = nil;
+  }
+
+  _alertWindow = nil;
+}
+
+@end