Help command for visible commands should be hidden

```
$ rails --help > tmp/before
$ bundle update rails
...
$ rails --help > tmp/after
$ diff -u tmp/before tmp/after
--- tmp/before	2019-04-19 00:12:08.000000000 -0700
+++ tmp/after	2019-04-19 00:14:55.000000000 -0700
@@ -52,7 +52,6 @@
   db:version
   destroy
   dev:cache
-  dev:help
   encrypted:edit
   encrypted:show
   initializers
```

1 files changed, 4 insertions, 2 deletions

diff --git a/railties/lib/rails/commands/dev/dev_command.rb b/railties/lib/rails/commands/dev/dev_command.rb
index a3f02f3172..9b2cb2b04a 100644
--- a/railties/lib/rails/commands/dev/dev_command.rb
+++ b/railties/lib/rails/commands/dev/dev_command.rb
@@ -5,8 +5,10 @@ require "rails/dev_caching"
 module Rails
   module Command
     class DevCommand < Base # :nodoc:
-      def help
-        say "rails dev:cache # Toggle development mode caching on/off."
+      no_commands do
+        def help
+          say "rails dev:cache # Toggle development mode caching on/off."
+        end
       end
 
       def cache