[HOTFIX] fix incorrect word in index-server doc
[HOTFIX] fix incorrect word in index-server doc

fix incorrect word in index-server doc

This closes #3390

jackylk/incubator-carbondata,jackylk/incubator-carbondata,zzcclp/carbondata,zzcclp/carbondata,jackylk/incubator-carbondata,zzcclp/carbondata,zzcclp/carbondata,jackylk/incubator-carbondata,zzcclp/carbondata