Don't attempt to load types with generic parameters as a module

This fixes an issue where custom ModuleBases that contained a generic
parameter would be loaded as a module - only to fail when trying to be
built.

Realistically, ModuleBases _should_ be abstract - but it was still a bug
that we allowed them to be included as a module.

src/Discord.Net.Commands/Builders/ModuleClassBuilder.cs

@@ -307,7 +307,8 @@ namespace Discord.Commands
         private static bool IsValidModuleDefinition(TypeInfo typeInfo)
         {
             return _moduleTypeInfo.IsAssignableFrom(typeInfo) &&
-                   !typeInfo.IsAbstract;
+                   !typeInfo.IsAbstract &&
+                   !typeInfo.ContainsGenericParameters;
         }
 
         private static bool IsValidCommandDefinition(MethodInfo methodInfo)