Broken link to app schema for integration-platform

### URL

https://github.com/getsentry/sentry/blob/master/src/sentry/api/validators/sentry_apps/schema.py

### Additional Info

At the bottom of the https://docs.sentry.io/organization/integrations/integration-platform/ui-components/stacktrace-link/

> For a more complete description of the grammar, see the source code.