Fix includes in source/scriptinterface

Make include-what-you-use happy with files in source/scriptinterface and
fix what needs to be fixed.

Ref: #8086
Signed-off-by: Ralph Sennhauser <ralph.sennhauser@gmail.com>

source/scriptinterface/ScriptExceptions.h

@@ -1,4 +1,4 @@
-/* Copyright (C) 2020 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -18,8 +18,6 @@
 #ifndef INCLUDED_SCRIPTEXCEPTIONS
 #define INCLUDED_SCRIPTEXCEPTIONS
 
-struct JSContext;
-class JSErrorReport;
 class ScriptRequest;
 
 namespace ScriptException