TestHashableCacheKey: Modernize hashing

Author: lorentey

TestFoundation/TestNSCache.swift

@@ -117,12 +117,15 @@ class TestNSCache : XCTestCase {
 
     class TestHashableCacheKey: Hashable {
         let string: String
-        var hashValue: Int { return string.hashValue }
 
         init(string: String) {
             self.string = string
         }
 
+        func hash(into hasher: inout Hasher) {
+            hasher.combine(string)
+        }
+
         static func ==(lhs: TestHashableCacheKey,
             rhs:TestHashableCacheKey) -> Bool {
             return lhs.string == rhs.string