Streams: better document the max node limits.

redis.conf

@@ -1110,7 +1110,10 @@ hll-sparse-max-bytes 3000
 # tree of big nodes that encode multiple items inside. Using this configuration
 # it is possible to configure how big a single node can be in bytes, and the
 # maximum number of items it may contain before switching to a new node when
-# appending new stream entries.
+# appending new stream entries. If any of the following settings are set to
+# zero, the limit is ignored, so for instance it is possible to set just a
+# max entires limit by setting max-bytes to 0 and max-entries to the desired
+# value.
 stream-node-max-bytes 4096
 stream-node-max-entires 100