timezone: Fix regression caused by #3361 (#3418)

Because of that PR, TimeZoneRule was bigger than 0x4000 thanks to a
misuse of a constant.

This commit address this issue and add a new unit test to ensure the size of
TimeZoneRule is 0x4000 bytes.

Also address suggestions that were lost on the original PR.

Ryujinx.Tests/Time/TimeZoneRuleTests.cs

@@ -0,0 +1,18 @@
+using NUnit.Framework;
+using Ryujinx.HLE.HOS.Services.Time.TimeZone;
+using System.Runtime.CompilerServices;
+
+namespace Ryujinx.Tests.Time
+{
+    internal class TimeZoneRuleTests
+    {
+        class EffectInfoParameterTests
+        {
+            [Test]
+            public void EnsureTypeSize()
+            {
+                Assert.AreEqual(0x4000, Unsafe.SizeOf<TimeZoneRule>());
+            }
+        }
+    }
+}