I need to delete the duty 'HRA_REOPEN_PERFORMANCE_DOCUMENT_BY_MANAGER_PRIV'

Hi experts, I need to delete the duty 'HRA_REOPEN_PERFORMANCE_DOCUMENT_BY_MANAGER_PRIV' from this role: Performance Management Line Manager. 

I noticed that this duty is inherited by this role, contained in another role, the one I actually use = Line Manager.

So I did it this way;

I made a copy of 'Performance Management Line Manager' role, working on this copy. I deleted from this role the HRA_REOPEN_PERFORMANCE_DOCUMENT_BY_MANAGER_PRIV and added this role directly to my Custom Line Manager. This isn't working anyway, because I always see the duty contained in the Performance Line Manager (standard role). Do I need to work on this standard role instead of making a copy of it?