docs: fix the type information in in-app-purchase (#12824)

Method returns Boolean, Manually confirmed the
correctness by running `npm run create-api-json`.

docs/api/in-app-purchase.md

@@ -30,7 +30,7 @@ The `inAppPurchase` module has the following methods:
 
 ### `inAppPurchase.canMakePayments()`
 
-Returns `true` if the user can make a payment and `false` otherwise.
+Returns `Boolean`, whether a user can make a payment.
 
 ### `inAppPurchase.getReceiptURL()`