Alphaplan: allow failure on import

Otherwise the parent pipeline is stuck in "running" state until the
manual action has been performed. See for reference:
https://gitlab.com/gitlab-org/gitlab/-/issues/361574

build-common.yml

@@ -277,6 +277,7 @@ workflow:
   stage: Alphaplan
   rules:
     - when: manual
+      allow_failure: true
   variables:
     # Most AP_WEBSERVICE_* variables are set in GitLab CI variables. We're defining the
     # URL here, though, so that it can be overridden in a job's variables block.