[testing] improve sanity check in jwt_token_creds interop test (#2513)

testassets/Shared/InteropClient.cs

@@ -238,7 +238,7 @@ private async Task<ChannelCredentials> CreateCredentialsAsync(bool? useTestCaOve
         if (options.TestCase == "jwt_token_creds")
         {
             var googleCredential = await GoogleCredential.GetApplicationDefaultAsync();
-            Assert.IsTrue(googleCredential.IsCreateScopedRequired);
+            Assert.IsFalse(googleCredential.UnderlyingCredential is ComputeCredential);
             credentials = ChannelCredentials.Create(credentials, googleCredential.ToCallCredentials());
         }