erp5_web: Remove File and Image from allowed content type list

bt5/erp5_web/bt/template_portal_type_allowed_content_type_list

 Web Page Module | Web Page
 Web Page | Embedded File
-Web Section | File
-Web Section | Image
 Web Section | Role Definition
 Web Section | Web Section
 Web Site Module | Web Site
-Web Site | File
-Web Site | Image
 Web Site | Role Definition
 Web Site | Web Section
\ No newline at end of file