BLS signatures: bug fix in test, removed unnecessary function, added new test

packages/binary/valuetransfer/address/signaturescheme/bls_test.go

 package signaturescheme
 
 import (
+	"github.com/magiconair/properties/assert"
 	"github.com/mr-tron/base58"
 	"testing"
-
-	"github.com/magiconair/properties/assert"
 )
 
 var dataToSign = []byte("Hello Boneh-Lynn-Shacham (BLS) --> Boneh-Drijvers-Neven (BDN)")