officejs_ooffice: fix non existant appcache on web sites

This caused upgrader errors such as:

    Error: Web Site web_site_module/ooffice_spreadsheet references a non existant appcache gadget_officejs_spreadsheet.appcache
3 jobs for fix/officejs_smart_assistant_non_existant_appcache in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-TestRunner1

01:27:53

passed ERP5.PerformanceTest-TestRunner1

00:32:27

failed ERP5.UnitTest-TestRunner1

01:53:06