[DOCS] Genericize 'reserved words' topic
[DOCS] Genericize 'reserved words' topic

Replace a couple of github URLs in comments,
used for figuring out when/how to update this
page based on source code changes.

Reword a 'Cloudera recommends' reference.

Change-Id: I04020aad6f0c468a354f94934dd4b93d2d5a75f1
Reviewed-on: http://gerrit.cloudera.org:8080/6364
Reviewed-by: Ambreen Kazi <e1177c5e2e2eee99dbd6ef5fbe233f66bddb1c06@cloudera.com>
Reviewed-by: John Russell <308573a947c636ab812b35943b6242633bef8113@cloudera.com>
Tested-by: Impala Public Jenkins

cloudera/Impala,michaelhkw/incubator-impala,cloudera/Impala,michaelhkw/incubator-impala,cloudera/Impala,michaelhkw/incubator-impala,michaelhkw/incubator-impala,michaelhkw/incubator-impala,cloudera/Impala,cloudera/Impala,michaelhkw/incubator-impala,cloudera/Impala,michaelhkw/incubator-impala,cloudera/Impala