org-agenda-hide-tags-regexp

org-agenda-hide-tags-regexp is a variable defined in `org-agenda.el'.
Its value is

nil

Documentation:
Regular expression used to filter away specific tags in agenda views.
This means that these tags will be present, but not be shown in the agenda
line. Secondary filtering will still work on the hidden tags.
Nil means don't hide any tags.

You can customize this variable.