Changes service log from error to warning.

Updates the service log message from an error to a warning
when a service version change is detected. This prevents
unnecessary alarm about expected behavior during upgrades.

Author: webprofusion-chrisc

src/Certify.Core/Management/CertifyManager/CertifyManager.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.IO;
@@ -270,7 +270,7 @@ private async void _frequentTimer_Elapsed(object sender, System.Timers.ElapsedEv
 
         private async Task PerformServiceUpgrades()
         {
-            _serviceLog?.Error($"Service version has changed. Performing upgrade checks.");
+            _serviceLog?.Warning($"Service version has changed. Performing upgrade checks.");
 
             try
             {