config: fix litecoin simnet mode

This commit fixes a bug where it was impossible to run lnd in litecoin's
simnet mode because of code duplication. As a result `numNets > 1`
conditional was always true when running lnd with `cfg.Litecoin.SimNet`
flag.

config.go

@@ -647,10 +647,6 @@ func loadConfig() (*config, error) {
 			numNets++
 			ltcParams = litecoinTestNetParams
 		}
-		if cfg.Litecoin.SimNet {
-			numNets++
-			ltcParams = litecoinSimNetParams
-		}
 		if cfg.Litecoin.RegTest {
 			numNets++
 			ltcParams = litecoinRegTestNetParams