Plugins: Tidy up CLI code (#67723)

* remove dead code and use pkg/plugins for uninstall process

* fix linter

* remove unnecessary cruft

pkg/cmd/grafana-cli/commands/remove_command.go

@@ -9,7 +9,7 @@ import (
 	"github.com/grafana/grafana/pkg/cmd/grafana-cli/utils"
 )
 
-func (cmd Command) removeCommand(c utils.CommandLine) error {
+func removeCommand(c utils.CommandLine) error {
 	pluginID := c.Args().First()
 	if pluginID == "" {
 		return errors.New("missing plugin parameter")