Add session replay breaking change to migration guide

Author: andreiborza

docs/platforms/javascript/common/migration/v9-to-v10.mdx

@@ -53,6 +53,10 @@ The removal entails **no breaking API changes**. However, in rare cases, you mig
 - If you set up Sentry Alerts that depend on FID, be aware that these could trigger once you upgrade the SDK, due to a lack of new values.
   To replace them, adjust your alerts (or dashbaords) to use INP.
 
+## Removed `_experiments.autoFlushOnFeedback` for Session Replays
+
+The `_experiments.autoFlushOnFeedback` option was removed and is now default behavior.
+
 </PlatformCategorySection>
 
 ## Removed APIs