IMPALA-6303: [DOCS] Fix incorrect mention of DataNodes
IMPALA-6303: [DOCS] Fix incorrect mention of DataNodes

The documentation on Impala Components (https://impala.apache.org/
docs/build/html/topics/impala_components.html) incorrectly states
"... catalog service relays the metadata changes from Impala SQL
statements to all the DataNodes in a cluster ...", which is not
correct. It should be Impala daemons, instead of 'DataNodes'"

Change-Id: I2116b1f78ef6fa89eafe2126034699d2961c06f6
Reviewed-on: http://gerrit.cloudera.org:8080/9160
Reviewed-by: Michael Brown <97e4d5d0e400e5ad37382425ea95bde8b3933403@cloudera.com>
Tested-by: Impala Public Jenkins

cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala