Remove "fork_targets_finder_with_parents" feature flag
What does this MR do and why?
Contributes to #442392 (closed)
Problem
#search
in ForkTargetsFinder does not use the full namespace path name
for search. It only queries current namespace name. It prevents users
from searching by the full namespace path.
Workaround
When user requests a search by the full path. We can take the last part of it and search by group's name.