rabbitmq_cli: Fix typo in an error message in join_cluster

(cherry picked from commit 58c609c)

Author: dumbbell

deps/rabbitmq_cli/lib/rabbitmq/cli/ctl/commands/join_cluster_command.ex

@@ -78,7 +78,7 @@ defmodule RabbitMQ.CLI.Ctl.Commands.JoinClusterCommand do
 
   def output({:error, {:node_type_unsupported, db, node_type}}, %{node: _node_name}) do
     {:error, RabbitMQ.CLI.Core.ExitCodes.exit_software(),
-     "Error: `#{node_type}` node type is unsupported by the #{db} by database engine"}
+     "Error: `#{node_type}` node type is unsupported by the #{db} database engine"}
   end
 
   def output(