Register CLI commands implicitly

This patch removes the explicit `commands.AddCommands` function and
instead relies upon the `internal/commands` package which registers each
CLI command using `init()` instead.

Signed-off-by: Alano Terblanche <18033717+Benehiko@users.noreply.github.com>

cli/command/plugin/cmd.go

@@ -3,9 +3,14 @@ package plugin
 import (
 	"github.com/docker/cli/cli"
 	"github.com/docker/cli/cli/command"
+	"github.com/docker/cli/internal/commands"
 	"github.com/spf13/cobra"
 )
 
+func init() {
+	commands.Register(newPluginCommand)
+}
+
 // NewPluginCommand returns a cobra command for `plugin` subcommands
 //
 // Deprecated: Do not import commands directly. They will be removed in a future release.