config: update docs for num-restricted-slots

sample-lnd.conf

@@ -566,7 +566,8 @@
 ; the headers of an HTTP request.
 ; http-header-timeout=5s
 
-; The number of restricted slots the server will allocate for peers.
+; The max number of incoming connections allowed in the server. Outbound
+; connections are not restricted.
 ; num-restricted-slots=100
 
 ; If true, a peer will *not* be disconnected if a pong is not received in time