exec shell: remove shell config or option

The option is never worked and can't properly work because almost all containers anyway using Ash/Dash from /bin/sh

main.go

@@ -46,7 +46,6 @@ func main() {
 		invertFlag      = flag.Bool("i", false, "invert default colors")
 		scaleCpu        = flag.Bool("scale-cpu", false, "show cpu as % of system total")
 		connectorFlag   = flag.String("connector", "docker", "container connector to use")
-		defaultShell    = flag.String("shell", "", "exec shell to use")
 	)
 	flag.Parse()
 
@@ -91,10 +90,6 @@ func main() {
 		config.Toggle("scaleCpu")
 	}
 
-	if *defaultShell != "" {
-		config.Update("shell", *defaultShell)
-	}
-
 	// init ui
 	if *invertFlag {
 		InvertColorMap()