fix: Removes support for v4 Client and old gump packet. (#1739)

### Summary
* Removes old gump packet support
* Removes support for v4 clients
* Removes `Unpack` flag and assumes it is always true.
* Removes StringToBuffer since this is built into .NET now.

> [!Note]
> View the file changes with white space off: https://github.com/modernuo/ModernUO/pull/1739/files?diff=split&w=1

Projects/Server/Network/NetState/ProtocolChanges.cs

@@ -23,7 +23,7 @@ public enum ProtocolChanges
     None = 0x00000000,
     NewSpellbook = 0x00000001,
     DamagePacket = 0x00000002,
-    Unpack = 0x00000004,
+    // Unpack = 0x00000004,
     BuffIcon = 0x00000008,
     NewHaven = 0x00000010,
     ContainerGridLines = 0x00000020,
@@ -38,9 +38,7 @@ public enum ProtocolChanges
     UltimaStore = 0x00004000,
     EndlessJourney = 0x00008000,
 
-    Version400a = NewSpellbook,
-    Version407a = Version400a | DamagePacket,
-    Version500a = Version407a | Unpack,
+    Version500a = NewSpellbook | DamagePacket /* | Unpack*/,
     Version502b = Version500a | BuffIcon,
     Version6000 = Version502b | NewHaven,
     Version6017 = Version6000 | ContainerGridLines,