redpanda: Recommend rpk config set

Redpanda suggests:
```
INFO  2022-11-23 15:00:11,965 [shard 0] main - application.cc:543 - Node configuration properties:
INFO  2022-11-23 15:00:11,965 [shard 0] main - application.cc:544 - (use `rpk config set <cfg> <value>` to change)
```
When the `rpk config set` is used the following log appears:
```
Command "set" is deprecated, use "rpk redpanda config set" instead
```

Signed-off-by: Ben Pope <ben@redpanda.com>
(cherry picked from commit bfbfe88)

src/v/redpanda/application.cc

@@ -553,7 +553,7 @@ void application::hydrate_config(const po::variables_map& cfg) {
     config_printer("redpanda", config::shard_local_cfg());
 
     vlog(_log.info, "Node configuration properties:");
-    vlog(_log.info, "(use `rpk config set <cfg> <value>` to change)");
+    vlog(_log.info, "(use `rpk redpanda config set <cfg> <value>` to change)");
     config_printer("redpanda", config::node());
 
     if (config["pandaproxy"]) {