Change explicit type to var in host creation

The explicit type IHost used in the creation of the host in Program.cs has been changed to implicit type 'var'. This simplifies the code and aids readability without any loss of clarity or efficiency.

Quartz.Impl.RavenStore.Example/Program.cs

@@ -2,7 +2,7 @@
 using Quartz.Impl.RavenJobStore;
 using Quartz.Impl.RavenStore.Example;
 
-IHost host = Host.CreateDefaultBuilder(args)
+var host = Host.CreateDefaultBuilder(args)
     .ConfigureServices(services =>
     {
         services.AddHostedService<Worker>();