Delay the Cloudflare cache purge so that pages:deploy is finished

My tests indicate that the pages:deploy job typically takes 50-60
seconds to complete, so I'm delaying the cache purge for 180 seconds

.gitlab-ci.yml

@@ -84,6 +84,7 @@ purge-cache:
       for f in $(find public -type f); do FILES="$FILES,\"$CI_PAGES_URL/${f#public/}\""; done;
       FILES="$FILES] }"
     - echo $FILES
+    - sleep 180s # Give pages:deploy time to finish so the old pages don't get re-cached
     - >-
       wget -qO- "https://api.cloudflare.com/client/v4/zones/$CF_PURGE_CACHE_ZONE/purge_cache"
       --header "Content-Type: application/json"