docs: Fix v7 migration link (#14629)

Author: phthhieu

docs/changelog/v7.md

@@ -3714,7 +3714,7 @@ requires changes to certain configuration options or custom clients/integrations
 a version of [self-hosted Sentry](https://develop.sentry.dev/self-hosted/) (aka onpremise) older than `20.6.0` then you
 will need to [upgrade](https://develop.sentry.dev/self-hosted/releases/).**
 
-For detailed overview of all the changes, please see our [v7 migration guide](./MIGRATION.md#upgrading-from-6x-to-7x).
+For detailed overview of all the changes, please see our [v7 migration guide](/docs/migration/v6-to-v7.md).
 
 ### Breaking Changes