docs: update location of devtoolset-3 repo rpm
docs: update location of devtoolset-3 repo rpm

The old location is now returning a 404 error.

Despite the difference in package name, the contents (a single file in
/etc/yum.repos.d) appear to be identical.

Change-Id: I5bea09ddd83d8d1bd4f0e56c7aaf693ef96110af
Reviewed-on: http://gerrit.cloudera.org:8080/5506
Reviewed-by: Dan Burkert <4ef91e292a55314d2653d35ff669a6bd939ce515@apache.org>
Tested-by: Kudu Jenkins

InspurUSA/kudu,cloudera/kudu,helifu/kudu,InspurUSA/kudu,helifu/kudu,EvilMcJerkface/kudu,helifu/kudu,helifu/kudu,andrwng/kudu,helifu/kudu,InspurUSA/kudu,helifu/kudu,EvilMcJerkface/kudu,EvilMcJerkface/kudu,InspurUSA/kudu,andrwng/kudu,InspurUSA/kudu,cloudera/kudu,helifu/kudu,andrwng/kudu,EvilMcJerkface/kudu,InspurUSA/kudu,cloudera/kudu,helifu/kudu,andrwng/kudu,andrwng/kudu,InspurUSA/kudu,andrwng/kudu,EvilMcJerkface/kudu,InspurUSA/kudu,cloudera/kudu,cloudera/kudu,EvilMcJerkface/kudu,andrwng/kudu,EvilMcJerkface/kudu,cloudera/kudu,InspurUSA/kudu,andrwng/kudu,cloudera/kudu,cloudera/kudu,EvilMcJerkface/kudu,cloudera/kudu,andrwng/kudu,helifu/kudu,EvilMcJerkface/kudu