lncli: rename value to amt in addinvoice command

docs/grpc/python.md

@@ -86,7 +86,7 @@ for invoice in stub.SubscribeInvoices(request):
 Now, create an invoice for your node at `localhost:10009`and send a payment to
 it from another node.
 ```bash
-$ lncli addinvoice --value=100
+$ lncli addinvoice --amt=100
 {
 	"r_hash": <R_HASH>,
 	"pay_req": <PAY_REQ>