Update deploy job

ci/deploy.gitlab-ci.yml

@@ -1,9 +1,14 @@
  # Push a nightly tag if the pipeline succeeded.
 deploy:tag:
   stage: deploy
+  image: ubuntu:latest
+  before_script:
+    - export DEBIAN_FRONTEND=noninteractive
+    - apt-get update -y
+    - apt-get install -y --no-install-recommends git
   script:
     - git tag nightly master
-    - git push https://sillyprof:$EIGEN_CI_ACCESS_TOKEN@gitlab.com/libeigen/eigen.git master tag nightly
+    - git push $EIGEN_CI_GIT_PUSH_URL master tag nightly
   tags:
     - linux
     - eigen-runner