operations: Fix error paths in CherryPick on custom hook error
While checking whether we can remove the PreReceiveError
field of the
UserCherryPick
response I stumbled upon one branch where we seemingly
still setting that field. As it turns out though we don't as the error
condition is accidentally handled twice, and as a result we would always
return the structured error as expected.
Fix the confused code by removing the redundant-and-wrong error handling.
Part of gitlab#375572 (closed).
Edited by Patrick Steinhardt