package/libreplaygain: use version friendly to release-monitoring

Update LIBREPLAYGAIN_VERSION to match what is returned by
https://release-monitoring.org/project/370816

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
(cherry picked from commit 558a25994b3ccab9b308bb667e464bdff0ab0d61)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libreplaygain/libreplaygain.mk

@@ -4,9 +4,9 @@
 #
 ################################################################################
 
-LIBREPLAYGAIN_VERSION = r475
+LIBREPLAYGAIN_VERSION = 475
 LIBREPLAYGAIN_SITE = http://files.musepack.net/source
-LIBREPLAYGAIN_SOURCE = libreplaygain_$(LIBREPLAYGAIN_VERSION).tar.gz
+LIBREPLAYGAIN_SOURCE = libreplaygain_r$(LIBREPLAYGAIN_VERSION).tar.gz
 # upstream doesn't ship configure
 LIBREPLAYGAIN_AUTORECONF = YES
 LIBREPLAYGAIN_INSTALL_STAGING = YES