Fix a typo of data_owner (#524)

Signed-off-by: Gordon <garyw@apache.org>
diff --git a/docs/access-control.md b/docs/access-control.md
index 08cfe4a..f94b2fa 100644
--- a/docs/access-control.md
+++ b/docs/access-control.md
@@ -93,7 +93,7 @@
 where each value `u` in the fact meets the condition that
 
 ```
-data_owern task_access_data.data u
+data_owner task_access_data.data u
 ```
 
 is in the terms database. `_` is called the query wild card and `<=` is the