Add cleanup stage

[skip ci]

.gitlab-ci.yml

 stages:
   - build-and-publish
   - deploy
+  - cleanup
 
 build-and-publish:
   stage: build-and-publish
@@ -25,7 +26,6 @@ deploy-test:
     - conda activate test
     - conda build ./conda-recipe
     - conda install --use-local --only-deps pyzebra -y
-    - conda build purge-all
     - sudo systemctl restart pyzebra-test.service
 
 deploy-prod:
@@ -41,3 +41,8 @@ deploy-prod:
     - conda activate prod
     - conda update pyzebra -y
     - sudo systemctl restart pyzebra-prod.service
+
+cleanup-job:
+  stage: cleanup
+  script:
+    - conda build purge-all