Refresh some incorrect links in pg_crc.c/h

Author: Vignesh C
Discussion: https://postgr.es/m/CALDaNm0LPk9vTGTBPBRv0=fX=94o4r6-DuBbHNeCN2AH5bufLw@mail.gmail.com

src/backend/utils/hash/pg_crc.c

@@ -5,7 +5,7 @@
  *
  * See Ross Williams' excellent introduction
  * A PAINLESS GUIDE TO CRC ERROR DETECTION ALGORITHMS, available from
- * http://www.ross.net/crc/download/crc_v3.txt or several other net sites.
+ * http://ross.net/crc/download/crc_v3.txt or several other net sites.
  *
  * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California

src/include/utils/pg_crc.h

@@ -5,7 +5,7 @@
  *
  * See Ross Williams' excellent introduction
  * A PAINLESS GUIDE TO CRC ERROR DETECTION ALGORITHMS, available from
- * http://www.ross.net/crc/ or several other net sites.
+ * http://ross.net/crc/ or several other net sites.
  *
  * We have three slightly different variants of a 32-bit CRC calculation:
  * CRC-32C (Castagnoli polynomial), CRC-32 (Ethernet polynomial), and a legacy