Remove mga 3 as it is EOL now.

library/mageia

@@ -3,4 +3,3 @@
 latest: git://github.com/juanluisbaptiste/docker-brew-mageia@603a75ec98dfd7c26ed85108b309d4e5f39ded91 4
 cauldron: git://github.com/juanluisbaptiste/docker-brew-mageia@603a75ec98dfd7c26ed85108b309d4e5f39ded91 cauldron
 4: git://github.com/juanluisbaptiste/docker-brew-mageia@603a75ec98dfd7c26ed85108b309d4e5f39ded91 4
-3: git://github.com/juanluisbaptiste/docker-brew-mageia@603a75ec98dfd7c26ed85108b309d4e5f39ded91 3