cmd/geth: update copyright year (#22099)

cmd/geth/main.go

@@ -218,7 +218,7 @@ func init() {
 	// Initialize the CLI app and start Geth
 	app.Action = geth
 	app.HideVersion = true // we have a command to print the version
-	app.Copyright = "Copyright 2013-2020 The go-ethereum Authors"
+	app.Copyright = "Copyright 2013-2021 The go-ethereum Authors"
 	app.Commands = []cli.Command{
 		// See chaincmd.go:
 		initCommand,