7.6 CLI page needs to be updated with 7.6 tools package info

https://staging.docs-test.couchbase.com/server/7.6/cli/cli-intro.html

1. Currently lists 7.2.0 server tools packages.  All of the 7.2.0 needs to be updated to 7.6.0.

2. In the version compatibility section at the bottom of the page – https://staging.docs-test.couchbase.com/server/7.6/cli/cli-intro.html#version-compatibility

update from:

The 7.2.0 cbimport, cbexport, and cbbackupmgr utilities can be run against the following Couchbase Server versions:

• 7.2.0
• 7.1.x
• 7.0.x

to:

The 7.6.0 cbimport, cbexport, and cbbackupmgr utilities can be run against the following Couchbase Server versions:

• 7.6.0
• 7.2.x
• 7.1.x
• 7.0.x