Build: typo on on_retry (#11014)

I found this on production.

https://read-the-docs.sentry.io/issues/4838648613/?project=148442&query=is%3Aunresolved+%21message%3A%22%21message%3A%22%21message%3A%22SystemExit%22+%21message%3A%22frame-ancestors%22&referrer=issue-stream&statsPeriod=14d&stream_index=0

readthedocs/projects/tasks/builds.py

@@ -689,7 +689,7 @@ def on_retry(self, exc, task_id, args, kwargs, einfo):
 
             # Grab the format values from the exception in case it contains
             format_values = exc.format_values if hasattr(exc, "format_values") else None
-            self.data.director.attach_notification(
+            self.data.build_director.attach_notification(
                 BuildMaxConcurrencyError.LIMIT_REACHED,
                 format_values=format_values,
             )