Allow check job to fail

This makes merging a project MR possible even if the manifest has
received new commits since the MR pipeline build has run. The developer
is responsible for deciding whether it is safe to merge it without
having a build based on the latest manifest.

BCS 746-000794

common.yml

@@ -64,6 +64,7 @@ yamllint:
     # Explicitly allow externally triggered pipelines in every case
     - if: $CI_PIPELINE_SOURCE == "pipeline" || $CI_PIPELINE_SOURCE == "api"
   needs: ["integrate"]
+  allow_failure: true
   script:
     - cd ${CI_PROJECT_DIR}
     # When running in a trigger pipeline the CII_MERGE_REQUEST_IID is not set