ci: Build frappe assets

- Build frappe assets since it is used for print views
diff --git a/.github/helper/install.sh b/.github/helper/install.sh
index 7b0f944..f7a7122 100644
--- a/.github/helper/install.sh
+++ b/.github/helper/install.sh
@@ -44,3 +44,4 @@
 bench get-app erpnext "${GITHUB_WORKSPACE}"
 bench start &
 bench --site test_site reinstall --yes
+bench build --app frappe