Revert "add logging information for configuration error (#79)" (#80)

This reverts commit 9725a61.

Author: NihalHarish

src/main/java/com/amazon/opendistroforelasticsearch/security/auth/BackendRegistry.java

@@ -431,7 +431,6 @@ public boolean authenticate(final RestRequest request, final RestChannel channel
 
                 if(authDomain.isChallenge() && httpAuthenticator.reRequestAuthentication(channel, null)) {
                     auditLog.logFailedLogin("<NONE>", false, null, request);
-                    log.warn("The first challenge authentication method is {}, other methods with lower order may not work.",httpAuthenticator.getType());
                     log.trace("No 'Authorization' header, send 401 and 'WWW-Authenticate Basic'");
                     return false;
                 } else {