Correct build script.

.gitlab-ci.yml

@@ -18,7 +18,7 @@ pages:
   stage: deploy
   script:
     - cp -r site .public
-    - sed -ei "s/%DATE%/$(date +'%Y-%m-%d %H:%M')/g" .public/index.html
+    - sed -i -e "s/%BUILDDATE%/$(date +'%Y-%m-%d %H:%M')/g" .public/index.html
     - cp build/safelinks-cleaner-thunderbird.xpi .public
     - cp build/safelinks-cleaner-firefox.xpi .public
     - mv .public public