[#42] common: Replace Ballot struct's definition to vote.go src file

Remove empty ballot.go source file.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

common/ballot.go

@@ -1,12 +0,0 @@
-package common
-
-type Ballot struct {
-	// ID of the voting decision.
-	ID []byte
-
-	// Public keys of already voted inner ring nodes.
-	Voters [][]byte
-
-	// Height of block with the last vote.
-	Height int
-}

common/vote.go

@@ -7,6 +7,17 @@ import (
 	"github.com/nspcc-dev/neo-go/pkg/interop/util"
 )
 
+type Ballot struct {
+	// ID of the voting decision.
+	ID []byte
+
+	// Public keys of already voted inner ring nodes.
+	Voters [][]byte
+
+	// Height of block with the last vote.
+	Height int
+}
+
 const voteKey = "ballots"
 
 const blockDiff = 20 // change base on performance evaluation