Fix CI release pipeline for changelog and promotion

Now that the CHANGELOG generation and the release promotion tasks are
using external container images to perform tasks, we should not rely on
the ci-image to execute them.

Author: bclozel

ci/pipeline.yml

@@ -153,7 +153,6 @@ jobs:
         download_artifacts: false
         save_build_info: true
     - task: promote
-      image: ci-image
       file: git-repo/ci/tasks/promote-version.yml
       params:
         RELEASE_TYPE: M
@@ -203,7 +202,6 @@ jobs:
         download_artifacts: false
         save_build_info: true
     - task: promote
-      image: ci-image
       file: git-repo/ci/tasks/promote-version.yml
       params:
         RELEASE_TYPE: RC