Install git when doing a release

Apparently the reason releases did not have patch notes attached was
that git was not installed in the release-cli image at all.

.gitlab-ci.yml

@@ -59,6 +59,8 @@ release:
   image: registry.gitlab.com/gitlab-org/release-cli:latest
   rules:
     - if: $CI_COMMIT_TAG
+  before_script:
+    - apk add git
   script:
     - echo "Creating a new release for tag $CI_COMMIT_TAG."
     - |