doc: Update cracklib URL

Author: Daniel Gustafsson <daniel@yesql.se>
Reviewed-by: Laurenz Albe <laurenz.albe@cybertec.at>
Discussion: https://www.postgresql.org/message-id/flat/f7266133-618a-0adc-52ef-f43c78806b0e%402ndquadrant.com

doc/src/sgml/passwordcheck.sgml

@@ -25,7 +25,7 @@
  <para>
   You can adapt this module to your needs by changing the source code.
   For example, you can use
-  <ulink url="https://sourceforge.net/projects/cracklib/">CrackLib</ulink>
+  <ulink url="https://github.com/cracklib/cracklib">CrackLib</ulink>
   to check passwords &mdash; this only requires uncommenting
   two lines in the <filename>Makefile</filename> and rebuilding the
   module.  (We cannot include <productname>CrackLib</productname>