`doorstop remove` does not remove inactive requirements

[sevendays]

Steps:

• Edit the requirement set in Excel, using the active column to invalidate requirements, e.g. REQ999
• Publish the whole requirements with doorstop publish all build/requirements
• This warning appears: WARNING: no item with UID: REQ999 (the warning does not appear when publishing a single requirement set though).
• Remove the invalidated requirements with doorstop remove REQ999

Expected outcome:

• the requirement is removed

Actual outcome:

• the requirement is still there building tree... ERROR: no item with UID: REQ999

[sebhub]

This is because Document.find_item() returns only active items.