fix(pricing): fix pricing query when max_quantity is null (#12981)

what: 

Prices when max_quantity value is null is accounted for when quantity is passed in context.

Co-authored-by: Oli Juhl <59018053+olivermrbl@users.noreply.github.com>

.changeset/dry-bikes-burn.md

@@ -0,0 +1,5 @@
+---
+"@medusajs/pricing": patch
+---
+
+fix(pricing): fix pricing query when max_quantity is null