Alter callsign regex to support BV400

src/WsjtxUtils.WsjtxMessages/QsoParsing/BaseOsoParser.cs

@@ -47,7 +47,7 @@ internal abstract class BaseOsoParser
             // prefix
             @"(?<callprefix>(?:(?:[A-PR-Z][A-Z]?)|(?:[2-9][A-Z]{1,2}))\d)" +
             // suffix
-            @"(?<callsuffix>\d{0,3}[A-Z]{1,8})" +
+            @"(?<callsuffix>\d{0,3}[A-Z]{0,8})" +
             // modifier
             @"(?<modifier>\/[\dA-Z]{1,4})?$",
             RegexOptions.Compiled);