Correct placeholder format in documentation for consistency

Author: NonSwag

content/docs/serviceio/placeholders.mdx

@@ -113,7 +113,7 @@ current-bank: "Your current bank: %serviceio_bank%"
   2. PlaceholderAPI is installed and enabled
   3. The relevant service provider (economy, permissions...) is installed and working
   4. ServiceIO has successfully detected and registered the service provider
-  5. There is no typo in the placeholder and it is properly used `%serviceio_<PLACEHOLDER>%`
+  5. There is no typo in the placeholder and it is properly used `%serviceio_<placeholder>%`
 </Callout>
 
 If a placeholder shows the literal placeholder text instead of the expected value, check your ServiceIO configuration and ensure the appropriate service providers are properly installed and configured.