Format +1 vote on label as Label+1

This matches the old behavior used in emails.

Continue to parse +1 for both Label+1 and bare Label.

Change-Id: Ic1cfc9ab15a515b12491975586fda20da41b0f2f

gerrit-server/src/main/java/com/google/gerrit/server/util/LabelVote.java

@@ -75,8 +75,6 @@ public class LabelVote {
   public String format() {
     if (value == (short) 0) {
       return '-' + name;
-    } else if (value == (short) 1) {
-      return name;
     } else if (value < 0) {
       return name + value;
     } else {