Output `docker swarm join` on a single line

This avoids issues when copy/pasting between different shells on
different OSes, which may not all support `\` as a continuation
character.

Fixes #32725

Signed-off-by: Dave Henderson <dhenderson@gmail.com>

cli/command/swarm/join_token.go

@@ -108,10 +108,10 @@ func printJoinCommand(ctx context.Context, dockerCli command.Cli, nodeID string,
 
 	if node.ManagerStatus != nil {
 		if worker {
-			fmt.Fprintf(dockerCli.Out(), "To add a worker to this swarm, run the following command:\n\n    docker swarm join \\\n    --token %s \\\n    %s\n\n", sw.JoinTokens.Worker, node.ManagerStatus.Addr)
+			fmt.Fprintf(dockerCli.Out(), "To add a worker to this swarm, run the following command:\n\n    docker swarm join --token %s %s\n\n", sw.JoinTokens.Worker, node.ManagerStatus.Addr)
 		}
 		if manager {
-			fmt.Fprintf(dockerCli.Out(), "To add a manager to this swarm, run the following command:\n\n    docker swarm join \\\n    --token %s \\\n    %s\n\n", sw.JoinTokens.Manager, node.ManagerStatus.Addr)
+			fmt.Fprintf(dockerCli.Out(), "To add a manager to this swarm, run the following command:\n\n    docker swarm join --token %s %s\n\n", sw.JoinTokens.Manager, node.ManagerStatus.Addr)
 		}
 	}
 

cli/command/swarm/testdata/jointoken-manager-rotate.golden

@@ -2,7 +2,4 @@ Successfully rotated manager join token.
 
 To add a manager to this swarm, run the following command:
 
-    docker swarm join \
-    --token manager-join-token \
-    127.0.0.1
-
+    docker swarm join --token manager-join-token 127.0.0.1

cli/command/swarm/testdata/jointoken-manager.golden

@@ -1,6 +1,3 @@
 To add a manager to this swarm, run the following command:
 
-    docker swarm join \
-    --token manager-join-token \
-    127.0.0.1
-
+    docker swarm join --token manager-join-token 127.0.0.1

cli/command/swarm/testdata/jointoken-worker.golden

@@ -1,6 +1,3 @@
 To add a worker to this swarm, run the following command:
 
-    docker swarm join \
-    --token worker-join-token \
-    127.0.0.1
-
+    docker swarm join --token worker-join-token 127.0.0.1