testing/monero: update source URL
somehow old URL no longer works
http://build.alpinelinux.org/buildlogs/build-edge-armhf/testing/monero/monero-0.17.2.3-r1.log
somehow old URL no longer works
http://build.alpinelinux.org/buildlogs/build-edge-armhf/testing/monero/monero-0.17.2.3-r1.log