fix(cells): Update Invoices and Customers index urls to cell-based (#107698)

The endpoints are now available, we should use them so we can remove the
old ones.

Author: kcons

static/gsAdmin/components/customerGrid.tsx

@@ -81,7 +81,7 @@ function CustomerGrid(props: Props) {
   return (
     <ResultGrid
       inPanel
-      isRegional
+      isCellScoped
       path="/_admin/customers/"
       method="GET"
       columns={[

static/gsAdmin/views/invoices.tsx

@@ -117,7 +117,7 @@ export default function Invoices() {
       </Panel>
       <ResultGrid
         inPanel
-        isRegional
+        isCellScoped
         path="/_admin/invoices/"
         endpoint="/invoices/"
         method="GET"