Remove broken alternate download link
Remove broken alternate download link

drone.io was useful in that it allowed public downloads (unlike CircleCI
where you have to login, even with a public GitHub account) but it
rejects the ~12 MB artifact size of Glowstone++ with SpongeAPI. Remove
it for now. TODO: find a better place to host public builds for download

jimmikaelkael/GlowstonePlusPlus,GlowstoneMC/GlowstonePlusPlus,LukBukkit/GlowstonePlusPlus,GreenBeard/GlowstonePlusPlus,BlazePowered/Blaze-Server,LukBukkit/GlowstonePlusPlus,GlowstoneMC/GlowstonePlusPlus,BlazePowered/Blaze-Server,LukBukkit/GlowstonePlusPlus,keke142/GlowstonePlusPlus,GlowstonePlusPlus/GlowstonePlusPlus,LukBukkit/GlowstonePlusPlus,GlowstonePlusPlus/GlowstonePlusPlus,jimmikaelkael/GlowstonePlusPlus,GlowstoneMC/GlowstonePlusPlus,keke142/GlowstonePlusPlus,GlowstonePlusPlus/GlowstonePlusPlus,GreenBeard/GlowstonePlusPlus,GreenBeard/GlowstonePlusPlus,keke142/GlowstonePlusPlus,Postremus/GlowstonePlusPlus,jimmikaelkael/GlowstonePlusPlus,Postremus/GlowstonePlusPlus,BlazePowered/Blaze-Server,jimmikaelkael/GlowstonePlusPlus,GlowstoneMC/GlowstonePlusPlus,keke142/GlowstonePlusPlus,Postremus/GlowstonePlusPlus,GreenBeard/GlowstonePlusPlus,BlazePowered/Blaze-Server,Postremus/GlowstonePlusPlus,GlowstonePlusPlus/GlowstonePlusPlus