fix deprecation warning in auth.py

Author: iddqdex

ydb/iam/auth.py

@@ -43,8 +43,8 @@
 def get_jwt(account_id, access_key_id, private_key, jwt_expiration_timeout, algorithm, token_service_url, subject=None):
     assert jwt is not None, "Install pyjwt library to use jwt tokens"
     now = time.time()
-    now_utc = datetime.utcfromtimestamp(now)
-    exp_utc = datetime.utcfromtimestamp(now + jwt_expiration_timeout)
+    now_utc = datetime.fromtimestamp(now, datetime.UTC)
+    exp_utc = datetime.fromtimestamp(now + jwt_expiration_timeout, datetime.UTC)
     payload = {
         "iss": account_id,
         "aud": token_service_url,