Exclude Fivetran's incorrect Stripe customer discount records from SubPlat ETLs. (#6443)

sql/moz-fx-data-shared-prod/stripe_external/customer_discount_v1/query.sql

@@ -12,3 +12,6 @@ SELECT
   subscription_id,
 FROM
   `moz-fx-data-bq-fivetran`.stripe.customer_discount
+WHERE
+  -- Fivetran used to have a bug where it synced subscription discounts as customer discounts.
+  subscription_id IS NULL

sql/moz-fx-data-shared-prod/stripe_external/discount_v1/query.sql

@@ -17,3 +17,6 @@ SELECT
   subscription_id,
 FROM
   `moz-fx-data-bq-fivetran.stripe.discount`
+WHERE
+  -- Fivetran used to have a bug where it synced subscription discounts as customer discounts.
+  NOT (type = 'CUSTOMER' AND subscription_id IS NOT NULL)