Update FirebaseStorage/Sources/Storage.swift

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: morganchen12

FirebaseStorage/Sources/Storage.swift

@@ -249,7 +249,7 @@ import FirebaseCore
     private var instances: [String: Storage] = [:]
 
     /// Lock to manage access to the instances array to avoid race conditions.
-    private let instancesLock = OSAllocatedUnfairLock
+private let instancesLock = OSAllocatedUnfairLock()
 
     private init() {}