Fixed a typo in mailing list page.
Fixed a typo in mailing list page.

apache/incubator-tajo,gruter/tajo-cdh,gruter/tajo-cdh,gruter/tajo-cdh,yeeunshim/tajo_test,yeeunshim/tajo_test,yeeunshim/tajo_test,apache/incubator-tajo,apache/incubator-tajo,gruter/tajo-cdh,apache/incubator-tajo,yeeunshim/tajo_test