Change remove_replaced_entries to not verify replaced exists

remove_replaced_entries only removed an entry if the replacement item
existed in the collection. If an entry was updated prior to being
deleted then the "update" lingered in the database and the entry would
keep showing up on page refresh because the original (the replaced
entry) had been deleted. Removing this logic check ensures that only
original entries show up in the feed.
Revert "Change remove_replaced_entries to not verify replaced exists"

This reverts commit b9c4ea7e1da4b27ad9e57bd66fde779fd8143842.
Add mode parameter to remove_replace_entries

remove_replaced_entries only removed an entry if the replacement item
existed in the collection which caused problems on page load when all
entries are handled. Since deleting an entry only removes the original,
any update records are left lingering and would display since the
original could not be found. Added a "mode" parameter to help
differentiate between the two states.