fixed broken link to postgresql docs

Signed-off-by: NSantiago Pastorino <santiago@wyeworks.com>

activerecord/lib/active_record/locking/pessimistic.rb

@@ -40,7 +40,7 @@ module Locking
     #
     # Database-specific information on row locking:
     #   MySQL: http://dev.mysql.com/doc/refman/5.1/en/innodb-locking-reads.html
-    #   PostgreSQL: http://www.postgresql.org/docs/8.1/interactive/sql-select.html#SQL-FOR-UPDATE-SHARE
+    #   PostgreSQL: http://www.postgresql.org/docs/current/interactive/sql-select.html#SQL-FOR-UPDATE-SHARE
     module Pessimistic
       # Obtain a row lock on this record. Reloads the record to obtain the requested
       # lock. Pass an SQL locking clause to append the end of the SELECT statement