fix: use ## comments in empty-doc test (spec 0.5.0: single # is content)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: PHPCraftdream

tests/Ktav.Tests/BasicTests.cs

@@ -170,7 +170,7 @@ public void LoadsEmptyDocumentDefaultsToObject()
         Assert.That(v, Is.InstanceOf<KtavObject>());
         Assert.That(((KtavObject)v).Entries, Is.Empty);
 
-        var v2 = Ktav.Loads("# just a comment\n# another\n");
+        var v2 = Ktav.Loads("## just a comment\n## another\n");
         Assert.That(v2, Is.InstanceOf<KtavObject>());
         Assert.That(((KtavObject)v2).Entries, Is.Empty);
     }