fix: double check that an MR is not wip before assigning

it seems that filtering in the search is not enough, and some MR may be wip,
even when the 'wip="no"' parameter is given.

Let' skip WIP merge requests
2 jobs for topic/default/skip-wip in 43 seconds (queued for 29 seconds)
Status Job ID Name Coverage
  Lint
passed #72613
lint_black

00:00:43

passed #72614
lint_flake8

00:00:22