Remove 2015.03 from supported versions

It won't be receiving any updates

library/rakudo-star

@@ -1,6 +1,5 @@
 # maintainer: Rob Hoelz <rob AT hoelz.ro> (@hoelzro)
 
 2015.05:  git://github.com/perl6/docker@1590c9763cfeff123e6ab7991a49d4f3ba06661a
-2015.03:  git://github.com/perl6/docker@4250489944483969ff68d94476bfd81e0a2170ce
 
 latest:  git://github.com/perl6/docker@1590c9763cfeff123e6ab7991a49d4f3ba06661a