Remove out-of-date RM/Kerberos advice

All features should now work with Kerberos. I think
this is also referring to the old LLAMA integration,
so is doubly out-of-date.

Change-Id: If668c80cb77e55ebdea5815c4b7f52155a466004
Reviewed-on: http://gerrit.cloudera.org:8080/12214
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
Reviewed-by: Bikramjeet Vig <bikramjeet.vig@cloudera.com>

docs/topics/impala_kerberos.xml

@@ -83,10 +83,6 @@ under the License.
           <xref href="http://web.mit.edu/Kerberos/krb5-1.8/" scope="external" format="html"> Kerberos
           documentation</xref>.
         </p>
-        <p rev="1.2">
-          Currently, you cannot use the resource management feature on a cluster that has Kerberos
-          authentication enabled.
-        </p>
       </note>
 
       <p>