(bug 47496) Use (hidden) preference for copyright acknowledgment

Created hidden preference for copyright acknowledgment

Removed code added/refactored in https://gerrit.wikimedia.org/r/89859 as it breaks preferences here.

Change-Id: I61c5a155ac41c9b799095212d9b8243fc1bfbbca
Merge "(bug 47496) Use (hidden) preference for copyright acknowledgment"