Fix test after log message changed

Author: nicktindall

server/src/test/java/org/elasticsearch/cluster/routing/allocation/allocator/DesiredBalanceReconcilerTests.java

@@ -1528,7 +1528,7 @@ public Decision canAllocate(ShardRouting shardRouting, RoutingNode node, Routing
                 "Should log the NO decisions",
                 UndesiredAllocationsTracker.class.getCanonicalName(),
                 Level.WARN,
-                "[" + shardToPreventMovement + "][0] cannot be allocated on node [data-node-2]: [NO(Blocks allocation on node 2)]"
+                "[" + shardToPreventMovement + "][0] allocation decision for node [data-node-2]: [NO(Blocks allocation on node 2)]"
             )
         );