Remove the "Explicit" tag that was conflicting with the "LongRunning"…

… category tag. Now the tests that are long running can be properly excluded using the category exclusion feature of NUnit.

src/test/csharp/MessageSelectorTest.cs

@@ -51,7 +51,7 @@ public class MessageSelectorTest : NMSTestSupport
 		/// Since this test can take a long time to run, it is marked as explicit.
 		/// </summary>
 		/// <param name="destinationName"></param>
-		[Test, Explicit]
+		[Test]
 		public void FilterIgnoredMessagesSlowConsumerTest(
 			[Values(QUEUE_DESTINATION_NAME, TOPIC_DESTINATION_NAME)]
 			string destinationName)