ZLPNotifications [nfc]: Remove trivial constantsToExport

Since the module doesn't have any constants to export. If it wants
to export any, we can always add the method back.

Also remove `requiresMainQueueSetup`, which (according to the linked
doc) was needed because we were implementing `constantsToExport`.

On my iPhone 13 Pro running iOS 16.1, the feature supported by this
module (alerting the user when Zulip notifications are disabled at
the system level) still works as expected.

Author: chrisbobbe

ios/ZulipMobile/ZLPNotifications.swift

@@ -4,15 +4,6 @@ import React.RCTBridgeModule
 
 @objc(ZLPNotifications)
 class ZLPNotifications: NSObject {
-  // For why we include this, see
-  //   https://reactnative.dev/docs/0.68/native-modules-ios#exporting-constants
-  @objc
-  static func requiresMainQueueSetup() -> Bool {
-    // Initialization may be done on any thread; we don't need access to
-    // UIKit.
-    return false
-  }
-
   /// Whether the app can receive remote notifications.
   // Ideally we could subscribe to changes in this value, but there
   // doesn't seem to be an API for that. The caller can poll, e.g., by
@@ -28,9 +19,4 @@ class ZLPNotifications: NSObject {
         resolve(settings.authorizationStatus == UNAuthorizationStatus.authorized)
       })
   }
-
-  @objc
-  func constantsToExport() -> [String: Any]! {
-    return [:]
-  }
 }