Fix use of sha256 in test

Author: alextwoods

services/signin/src/test/java/software/amazon/awssdk/services/signin/auth/internal/OnDiskTokenManagerTest.java

@@ -145,7 +145,7 @@ void unmarshalToken_whenMissingRequiredFields_raisesException() throws IOExcepti
 
     private Path tokenLocation(String loginSession) {
         try {
-            MessageDigest sha1 = MessageDigest.getInstance("sha256");
+            MessageDigest sha1 = MessageDigest.getInstance("SHA-256");
             sha1.update(loginSession.getBytes(StandardCharsets.UTF_8));
             String cacheKey = BinaryUtils.toHex(sha1.digest()).toLowerCase(Locale.ENGLISH);
             return tempDir.resolve(cacheKey + ".json");