bzip2: change upstream site

The bzip.org website is down. Use the Buildroot backup download site.
Remove the website link as there is no clear alternative upstream at
this point.

  https://lwn.net/Articles/762264/

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/bzip2/Config.in

@@ -5,5 +5,3 @@ config BR2_PACKAGE_BZIP2
 	  It typically compresses files to within 10% to 15% of the best
 	  available techniques, while being around twice as fast at
 	  compression and six times faster at decompression.
-
-	  http://www.bzip.org

package/bzip2/bzip2.mk

@@ -5,7 +5,7 @@
 ################################################################################
 
 BZIP2_VERSION = 1.0.6
-BZIP2_SITE = http://www.bzip.org/$(BZIP2_VERSION)
+BZIP2_SITE = http://sources.buildroot.net
 BZIP2_INSTALL_STAGING = YES
 BZIP2_LICENSE = bzip2 license
 BZIP2_LICENSE_FILES = LICENSE