Seal/abstract/virtual everything (#6739)

Content.Server/Module/ServerModuleManager.cs

@@ -7,7 +7,7 @@ namespace Content.Server.Module
     /// Provides simple way for shared code to check if it's being run by
     /// the client of the server.
     /// </summary>
-    public class ServerModuleManager : IModuleManager
+    public sealed class ServerModuleManager : IModuleManager
     {
         bool IModuleManager.IsClientModule => false;
         bool IModuleManager.IsServerModule => true;