feat(crons): Add note about upsert endpoints (#7666)

src/platforms/common/crons/index.mdx

@@ -127,6 +127,13 @@ curl "${SENTRY_CRONS}?environment=dev&status=ok"
 
 Sentry enables the automatic creation or update of a monitor (upsert) through the check-in payload. This can be useful if you have many scheduled tasks or need to create them dynamically.
 
+<Note type="warning">
+
+In the future this feature will use the `ingest.sentry.io` style check in
+format and the `sentry.io/api` format will be deprecated.
+
+</Note>
+
 <SignInNote />
 
 ```bash {tabTitle: cURL}