/topics/sentinel-clients.md has outdated references and terminology, mentions non-existent google group

[stockholmux]

In pre-publishing review (#91) I noticed several issues with /topics/sentinel-clients.md

If the ROLE commands is not available (it was introduced in Redis OSS 2.8.12), a client may resort to the INFO replication command parsing the role: field of the output.

and

Starting with Redis OSS 2.8.12

Remove reference to 2.8.12

For additional information or to discuss specific aspects of this guidelines, please drop a message to the Valkey Google Group.

There isn't a Valkey Google group, so this should be deleted.

Finally, there are 44 references that need to be updated to primary

[zuiderkwast]

Addressing this, except "master" which I'm leaving for #148