fix C# build

src/csharp/Grpc.Core/VersionInfo.cs

@@ -41,6 +41,6 @@ namespace Grpc.Core
         /// <summary>
         /// Current version of gRPC C#
         /// </summary>
-        public const string CurrentVersion = "0.13.0-pre1";
+        public const string CurrentVersion = "0.13.0";
     }
 }

templates/src/csharp/Grpc.Core/VersionInfo.cs.template

@@ -43,6 +43,6 @@
           /// <summary>
           /// Current version of gRPC C#
           /// </summary>
-          public const string CurrentVersion = "${settings.csharp_version}";
+          public const string CurrentVersion = "${settings.version.major}.${settings.version.minor}.${settings.version.patch}";
       }
   }