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

@@ -884,7 +884,7 @@ In order to speedup the reconfiguration of other nodes, a pong packet is broadca
 
 The other nodes will detect that there is a new primary serving the same slots served by the old primary but with a greater `configEpoch`, and will upgrade their configuration. Replicas of the old primary (or the failed over primary if it rejoins the cluster) will not just upgrade the configuration but will also reconfigure to replicate from the new primary. How nodes rejoining the cluster are configured is explained in the next sections.
 
-### Masters reply to replica vote request
+### Primaries reply to replica vote request
 
 In the previous section, we discussed how replicas try to get elected. This section explains what happens from the point of view of a primary that is requested to vote for a given replica.