Update PlaceholderAPI link in requirements section

Author: NonSwag

content/docs/serviceio/placeholders.mdx

@@ -7,7 +7,7 @@ icon: Variable
 
 
 <Callout title="Requirements">
-  ServiceIO v2.3.0+ and [PlaceholderAPI](https://github.com/PlaceholderAPI/PlaceholderAPI) are required for placeholder support.
+  ServiceIO v2.3.0+ and [PlaceholderAPI](https://modrinth.com/project/lKEzGugV) are required for placeholder support.
 </Callout>
 
 ServiceIO provides PlaceholderAPI integration, allowing you to use ServiceIO data in other plugins that support placeholders.