CI: set “allow_failure: true” for the manual deploy job

Otherwise the pipeline will remain blocked until someone manually starts the
deploy job (see documentation of “rules” in Gitlab CI ref.).

.gitlab-ci.yml

@@ -113,6 +113,7 @@ deploy_julia:
   rules:
     - if: '$CI_PROJECT_NAMESPACE == "Dynare" && $CI_COMMIT_REF_NAME == "master"'
       when: manual
+      allow_failure: true
     - when: never
   script:
     - cp -R $CI_COMMIT_SHA /srv/www.dynare.org/preprocessor/