Add import

Author: yim-lee

Sources/PackageCollections/Providers/JSONPackageCollectionProvider.swift

@@ -10,6 +10,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+import _Concurrency
+
 import Basics
 import Dispatch
 import struct Foundation.Data

Sources/PackageCollectionsSigning/CertificatePolicy.swift

@@ -10,7 +10,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-import _Concurrency
 import Dispatch
 import Foundation