Maintenance: Fix the Zammad binary package build size.

script/build/cleanup.sh

@@ -15,6 +15,10 @@ rm .rspec
 rm -rf .storybook
 find app/frontend/ -name '*.stories.ts' -exec rm {} +
 
+# Remove our customized .yarnrc to let yarn use the global cache
+#   instead of .yarn/cache which would go into the packages.
+rm .yarnrc
+
 # CI
 rm -rf .github .gitlab
 rm .gitlab-ci.yml