Doc: fix bogus intarray index example.

The siglen parameter is provided by gist__intbig_ops not
gist__int_ops.

Simon Norris

Discussion: https://postgr.es/m/11BF2AA9-17AE-432A-AFE1-584FB9FB079D@hillcrestgeo.ca

doc/src/sgml/intarray.sgml

@@ -446,7 +446,7 @@
 CREATE TABLE message (mid INT PRIMARY KEY, sections INT[], ...);
 
 -- create specialized index with signature length of 32 bytes
-CREATE INDEX message_rdtree_idx ON message USING GIST (sections gist__int_ops(siglen=32));
+CREATE INDEX message_rdtree_idx ON message USING GIST (sections gist__intbig_ops (siglen = 32));
 
 -- select messages in section 1 OR 2 - OVERLAP operator
 SELECT message.mid FROM message WHERE message.sections && '{1,2}';