Omit deprecated gems from gem help commands

This change came about through discussion with David Rodgriguez. We've
been deliberating whether to document the deprecated status of commands.
I looked for examples in the OSS community and found that there's a lot
of inconsistency around documenting deprecated items. Ruby does and
doesn't do it. Rails seems to do it. Elixir seems to do it. It's not a
settled matter.

Ultimately, the decision was to remove the deprecated commands from the
`help commands` command.

lib/rubygems/commands/help_command.rb

@@ -332,6 +332,8 @@ def show_commands # :nodoc:
     @command_manager.command_names.each do |cmd_name|
       command = @command_manager[cmd_name]
 
+      next if command.deprecated?
+
       summary =
         if command
           command.summary

test/rubygems/test_gem_commands_help_command.rb

@@ -40,7 +40,9 @@ def test_gem_help_commands
 
     util_gem 'commands' do |out, err|
       mgr.command_names.each do |cmd|
-        assert_match(/\s+#{cmd}\s+\S+/, out)
+        unless mgr[cmd].deprecated?
+          assert_match(/\s+#{cmd}\s+\S+/, out)
+        end
       end
 
       if Gem::HAVE_OPENSSL
@@ -51,6 +53,17 @@ def test_gem_help_commands
     end
   end
 
+  def test_gem_help_commands_omits_deprecated_commands
+    mgr = Gem::CommandManager.new
+
+    util_gem 'commands' do |out, err|
+      deprecated_commands = mgr.command_names.select {|cmd| mgr[cmd].deprecated? }
+      deprecated_commands.each do |cmd|
+        refute_match(/\s+#{cmd}\s+\S+/, out)
+      end
+    end
+  end
+
   def test_gem_no_args_shows_help
     util_gem do |out, err|
       assert_match(/Usage:/, out)