Set correct appveyor version on release build
Set correct appveyor version on release build

bjornicus/confluent-kafka-dotnet,bjornicus/confluent-kafka-dotnet,MaximGurschi/rdkafka-dotnet,treziac/confluent-kafka-dotnet,MrGlenThomas/confluent-kafka-dotnet,treziac/confluent-kafka-dotnet,MrGlenThomas/confluent-kafka-dotnet,ah-/rdkafka-dotnet