erp5_xhtml_style: remove not needed cache

This case breaks action calculation between xhtml style and ERP5JS.
3 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-Master

01:18:54

failed ERP5.PerformanceTest-Master

00:24:08

failed ERP5.UnitTest-Master.Medusa

03:28:06