Update topics/cluster-spec.md

Co-authored-by: Madelyn Olson <madelyneolson@gmail.com>
Signed-off-by: Anastasia Alexandrova <anastasia.alexandrova@percona.com>

topics/cluster-spec.md

@@ -1050,7 +1050,7 @@ the independent failures of single nodes caused by hardware or software issues
 that can accumulate over time. For example:
 
 * Master A has a single replica A1.
-* Master A fails. A1 is promoted as new primary.
+* Primary A fails. A1 is promoted as new primary.
 * Three hours later A1 fails in an independent manner (unrelated to the failure of A). No other replica is available for promotion since node A is still down. The cluster cannot continue normal operations.
 
 If the map between primaries and replicas is fixed, the only way to make the cluster