Update link to signing secret documentation of Stripe

Closes #12442

modules/account_payment_stripe/doc/index.rst

@@ -22,7 +22,7 @@ webhook `signing secret`_ is set on the Account.
 If no webhook is setup, a cron task fetches the new events.
 
 .. _webhooks: https://stripe.com/docs/webhooks
-.. _`signing secret`: https://stripe.com/docs/webhooks/signatures
+.. _`signing secret`: https://dashboard.stripe.com/webhooks
 
 Customer
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