[UI] Fix serial and batch code generators (#9772)

* Tweak stock item form

- Fix batch code placeholder
- Fix serial number placeholder

* Tweak build output form

* More cleanup

* Fix for PurchaseOrderForm

* Refactoring placeholder values

docs/docs/settings/global.md

@@ -197,7 +197,6 @@ Configuration of stock item options
 | Name | Description | Default | Units |
 | ---- | ----------- | ------- | ----- |
 {{ globalsetting("SERIAL_NUMBER_GLOBALLY_UNIQUE") }}
-{{ globalsetting("SERIAL_NUMBER_AUTOFILL") }}
 {{ globalsetting("STOCK_DELETE_DEPLETED_DEFAULT") }}
 {{ globalsetting("STOCK_BATCH_CODE_TEMPLATE") }}
 {{ globalsetting("STOCK_ENABLE_EXPIRY") }}