docs: update example string (ory#1982)

Author: aeneasr

docs/kratos/social-signin/15_facebook.mdx

@@ -157,8 +157,8 @@ Follow these steps to add Facebook as a social sign-in provider to your project
              client_id: .... # Replace this with the OAuth2 Client ID provided by Facebook app
              client_secret: .... # Replace this with the OAuth2 Client Secret provided by Facebook app
              mapper_url: "base64://{YOUR_BASE64_ENCODED_JSONNET_HERE}"
-             # Alternatively, use an URL:
-             # mapper_url: https://storage.googleapis.com/abc-cde-prd/9cac9717f007808bf17f22ce7f4295c739604b183f05ac4afb4
+             # Alternatively, use an URL like this example
+             # mapper_url: https://storage.googleapis.com/example-example-prd/example-file
              scope:
                - email
              # required for email and email_verified claims in the near future