fix(dashboard): PL creation - customers table customers count (#9237)

**What**
- display the number of customers in a group in the price list create flow

---

CLOSES https://github.com/medusajs/medusa/issues/9210
FIXES CC-517

packages/admin/dashboard/src/routes/price-lists/common/components/price-list-customer-group-rule-form/price-list-customer-group-rule-form.tsx

@@ -59,9 +59,12 @@ export const PriceListCustomerGroupRuleForm = ({
     prefix: PREFIX,
   })
   const { customer_groups, count, isLoading, isError, error } =
-    useCustomerGroups(searchParams, {
+    useCustomerGroups(
-      placeholderData: keepPreviousData,
+      { ...searchParams, fields: "customers.id" },
-    })
+      {
+        placeholderData: keepPreviousData,
+      }
+    )
 
   const updater: OnChangeFn<RowSelectionState> = (value) => {
     const state = typeof value === "function" ? value(rowSelection) : value