Disable authentication check, but keep runnable

In this branch, we originally avoided the authentication check by
getting rid of the run method attached to the command.  Instead of that,
this commit makes the `gh actions` command runnable again, but the
authentication is disabled with `cmdutil.DisableAuthCheck`; this mirrors
what's done for `gh version`.

`gh actions` and `gh actions [-h | --help]` all work while being logged
out.

In addition, this commit restores some original behavior.  Before this
commit, the help footer (usage, inherited flags, etc.) is appended
whether you use `gh actions` or `gh actions --help`.  This commit
restores the original behavior where `gh actions` prints just the text
for the actions explanation, but `gh actions --help` appends the help
footer.

pkg/cmd/actions/actions.go

@@ -1,6 +1,8 @@
 package actions
 
 import (
+	"fmt"
+
 	"github.com/MakeNowJust/heredoc"
 	"github.com/cli/cli/pkg/cmdutil"
 	"github.com/cli/cli/pkg/iostreams"
@@ -14,11 +16,16 @@ func NewCmdActions(f *cmdutil.Factory) *cobra.Command {
 		Use:   "actions",
 		Short: "Learn about working with GitHub actions",
 		Long:  actionsExplainer(cs),
+		Run: func(cmd *cobra.Command, args []string) {
+			fmt.Fprintln(f.IOStreams.Out, actionsExplainer(cs))
+		},
 		Annotations: map[string]string{
 			"IsActions": "true",
 		},
 	}
 
+	cmdutil.DisableAuthCheck(cmd)
+
 	return cmd
 }