[docs] Update Impala links to the Apache docs/wiki
[docs] Update Impala links to the Apache docs/wiki

Change-Id: I77f02823f421ab801ac3b6a03cc69a4075c63c23
Reviewed-on: http://gerrit.cloudera.org:8080/9904
Tested-by: Kudu Jenkins
Reviewed-by: Adar Dembo <866ca730bfc7f544e3ebce604ceeba4879f23df0@cloudera.com>

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