Dropped test hlt2_light_reco_pr_kf_velo_open_without_UT_with_mcchecking testing for Velo Open

It was using an old MC sample not compatible with most recent code and was felt to not be useful anymore : "We can drop that test, the test only covers the performance with VELO open, not a specific reconstruction configuration. So existing other tests already cover this config. I hope we won't ever need to optimize this for VELO open anymore."