cmd, core: remove calaveras testnet (#23366)

Removes references to the short-lived Calaveras testnet

cmd/geth/main.go

@@ -138,7 +138,6 @@ var (
 		utils.RopstenFlag,
 		utils.RinkebyFlag,
 		utils.GoerliFlag,
-		utils.CalaverasFlag,
 		utils.VMEnableDebugFlag,
 		utils.NetworkIdFlag,
 		utils.EthStatsURLFlag,
@@ -278,9 +277,6 @@ func prepare(ctx *cli.Context) {
 	case ctx.GlobalIsSet(utils.GoerliFlag.Name):
 		log.Info("Starting Geth on Görli testnet...")
 
-	case ctx.GlobalIsSet(utils.CalaverasFlag.Name):
-		log.Info("Starting Geth on Calaveras testnet...")
-
 	case ctx.GlobalIsSet(utils.DeveloperFlag.Name):
 		log.Info("Starting Geth in ephemeral dev mode...")