Update broken link CQL reference in README.asc

patch by Alex Gaetano Padula; reviewed by Stefan Miklosovic for CASSANDRA-20823

Author: guycipher

README.asc

@@ -71,7 +71,7 @@ If your session looks similar to what's above, congrats, your single node
 cluster is operational!
 
 For more on what commands are supported by CQL, see
-http://cassandra.apache.org/doc/latest/cql/[the CQL reference]. A
+https://cassandra.apache.org/doc/4.0/cassandra/cql/[the CQL reference]. A
 reasonable way to think of it is as, "SQL minus joins and subqueries, plus collections."
 
 Wondering where to go from here?