Add onLoad gottcha note to next/script docs (#33097)

Add a note to the onLoad section of the next/script documentation clarifying that onLoad will not run if `strategy="beforeInteractive"`. (That tripped me up for a bit so I thought I'd update the docs to save any one else the hassle :).)

Co-authored-by: Lee Robinson <9113740+leerob@users.noreply.github.com>

docs/api-reference/next/script.md

@@ -46,6 +46,8 @@ The loading strategy of the script.
 
 A method that returns additional JavaScript that should be executed after the script has finished loading.
 
+> **Note: `onLoad` can't be used with the `beforeInteractive` loading strategy.**
+
 The following is an example of how to use the `onLoad` property:
 
 ```jsx