docs: Fix formatting of literal sections in fanotify docs

Stephen Rothwell reported the following warning was introduced by commit
c0baf9ac0b05 ("docs: Document the FAN_FS_ERROR event").

Documentation/admin-guide/filesystem-monitoring.rst:60: WARNING:
Definition list ends without a blank line; unexpected unindent.

Link: https://lore.kernel.org/r/[e-mail]
Reported-by: Stephen Rothwell <[e-mail]>
Signed-off-by: Gabriel Krisman Bertazi <[e-mail]>
Signed-off-by: Jan Kara <[e-mail]>

Documentation/admin-guide/filesystem-monitoring.rst

···
 
 A FAN_FS_ERROR Notification has the following format::
 
-  [ Notification Metadata (Mandatory) ]
-  [ Generic Error Record  (Mandatory) ]
-  [ FID record            (Mandatory) ]
+  ::
+
+     [ Notification Metadata (Mandatory) ]
+     [ Generic Error Record  (Mandatory) ]
+     [ FID record            (Mandatory) ]
 
 The order of records is not guaranteed, and new records might be added
 in the future.  Therefore, applications must not rely on the order and
···
 identified by ``struct fanotify_event_info_header.info_type`` being set
 to FAN_EVENT_INFO_TYPE_ERROR.
 
-  struct fanotify_event_info_error {
-	struct fanotify_event_info_header hdr;
-	__s32 error;
-	__u32 error_count;
-  };
+  ::
+
+     struct fanotify_event_info_error {
+          struct fanotify_event_info_header hdr;
+         __s32 error;
+         __u32 error_count;
+     };
 
 The `error` field identifies the type of error using errno values.
 `error_count` tracks the number of errors that occurred and were