lnwallet: increase legacy fee limit threshold to 1k sats

In this commit, we increase the legacy fee limit threshold (the amount
below which we'll allow 100% of funds to go to fees for the non-v2 RPC
calls) from 50 sats to 1k sats.

lnwallet/parameters.go

@@ -8,10 +8,13 @@ import (
 	"github.com/lightningnetwork/lnd/lnwire"
 )
 
-const (
+var (
 	// RoutingFee100PercentUpTo is the cut-off amount we allow 100% fees to
 	// be charged up to.
-	RoutingFee100PercentUpTo lnwire.MilliSatoshi = 50_000
+	RoutingFee100PercentUpTo = lnwire.NewMSatFromSatoshis(1_000)
+)
+
+const (
 
 	// DefaultRoutingFeePercentage is the default off-chain routing fee we
 	// allow to be charged for a payment over the RoutingFee100PercentUpTo