Update template

I found out that C# 10 added file-scoped namespaces that don't need the whole thing to be wrapped in braces, so that's neat.

src/Template.cs

@@ -1,5 +1,5 @@
-namespace aoc2021
-{
+namespace aoc2021;
+
 internal class DayTemplate
 {
     internal static void Go()
@@ -26,4 +26,3 @@
         Logger.Log($"part2: ");
     }
 }
-}