Revert "oOnly one system contacts fetch at a time."

This reverts commit d84e27f5a5f953fd68dbdf1086a75ffe6aee6720.

SignalMessaging/contacts/SystemContactsFetcher.swift

@@ -146,9 +146,6 @@ public class SystemContactsFetcher: NSObject {
     public private(set) var systemContactsHaveBeenRequestedAtLeastOnce = false
     private var hasSetupObservation = false
 
-    private var isFetching = false
-    private var hasQueuedFetch = false
-
     override init() {
         self.contactStoreAdapter = ContactsFrameworkContactStoreAdaptee()
 
@@ -235,7 +232,6 @@ public class SystemContactsFetcher: NSObject {
     @objc
     public func fetchOnceIfAlreadyAuthorized() {
         SwiftAssertIsOnMainThread(#function)
-
         guard authorizationStatus == .authorized else {
             return
         }
@@ -273,25 +269,11 @@ public class SystemContactsFetcher: NSObject {
             Logger.error("background task time ran out contacts fetch completed.")
         })
 
-        guard !isFetching else {
-            Logger.info("\(self.TAG) queuing contact fetch; contact fetch already in flight.")
-            hasQueuedFetch = true
-            return
-        }
-        isFetching = true
-
         // Ensure completion is invoked on main thread.
         let completion: (Error?) -> Void = { error in
             DispatchMainThreadSafe({
-                self.isFetching = false
-
                 completionParam?(error)
                 backgroundTask = nil
-
-                if self.hasQueuedFetch {
-                    self.hasQueuedFetch = false
-                    self.fetchOnceIfAlreadyAuthorized()
-                }
             })
         }