Make test comment a summary

csharp/src/Google.Protobuf.Test/GeneratedMessageTest.Proto2.cs

@@ -261,9 +261,11 @@ namespace Google.Protobuf
             Assert.True(message.IsInitialized());
         }
 
-        // Code was accidentally left in message parser that threw exceptions when missing required fields after parsing.
-        // We've decided to not throw exceptions on missing fields, instead leaving it up to the consumer how they
-        // want to check and handle missing fields.
+        /// <summary>
+        /// Code was accidentally left in message parser that threw exceptions when missing required fields after parsing.
+        /// We've decided to not throw exceptions on missing fields, instead leaving it up to the consumer how they
+        /// want to check and handle missing fields.
+        /// </summary>
         [Test]
         public void RequiredFieldsNoThrow()
         {