Fixes UIApplication.setMinimumBackgroundFetchInterval() deprecation warning

AltStore/AppDelegate.swift

@@ -15,6 +15,8 @@ import AltStoreCore
 import AltSign
 import Roxas
 
+extension UIApplication: LegacyBackgroundFetching {}
+
 extension AppDelegate
 {
     static let openPatreonSettingsDeepLinkNotification = Notification.Name("com.rileytestut.AltStore.OpenPatreonSettingsDeepLinkNotification")
@@ -246,7 +248,7 @@ extension AppDelegate
     private func prepareForBackgroundFetch()
     {
         // "Fetch" every hour, but then refresh only those that need to be refreshed (so we don't drain the battery).
-        UIApplication.shared.setMinimumBackgroundFetchInterval(1 * 60 * 60)
+        (UIApplication.shared as LegacyBackgroundFetching).setMinimumBackgroundFetchInterval(1 * 60 * 60)
         
         UNUserNotificationCenter.current().requestAuthorization(options: [.alert, .badge, .sound]) { (success, error) in
         }

AltStore/Types/DeprecatedAPIs.swift

@@ -1,5 +1,5 @@
 //
-//  PeekPopPreviewing.swift
+//  DeprecatedAPIs.swift
 //  AltStore
 //
 //  Created by Riley Testut on 3/2/23.
@@ -8,9 +8,15 @@
 
 import UIKit
 
-// Conforming UIViewControllers to PeekPopPreviewing allows us to call deprecated registerForPreviewing(with:sourceView:) without warnings.
+// Conform types to these protocols to call deprecated APIs without warnings.
+
 protocol PeekPopPreviewing
 {
     @discardableResult
     func registerForPreviewing(with delegate: UIViewControllerPreviewingDelegate, sourceView: UIView) -> UIViewControllerPreviewing
 }
+
+protocol LegacyBackgroundFetching
+{
+    func setMinimumBackgroundFetchInterval(_ minimumBackgroundFetchInterval: TimeInterval)
+}