remove deprecated builder/dockerignore
remove deprecated builder/dockerignore

This package was deprecated in de56a90929c5cde9697fc7c83f379cbddb21e323, which
was part of the 20.10 release, so consumers of this package should've been
able to migrate to the new location.

Signed-off-by: Sebastiaan van Stijn <64b2b6d12bfe4baae7dad3d018f8cbf6b0e7a044@gone.nl>

mahak/docker,Ramzec/docker,flavio/docker,bearstech/moby,nalind/docker,nalind/docker,thaJeztah/docker,nawawi/docker,konstruktoid/docker-upstream,flavio/docker,bearstech/moby,cpuguy83/docker,mahak/docker,jimjag/docker,Mokolea/docker,konstruktoid/docker-upstream,moby/moby,cpuguy83/docker,Ramzec/docker,trebonian/docker,thaJeztah/docker,cpuguy83/docker,moul/docker,mahak/docker,cpuguy83/docker,moby/moby,vdemeester/docker,thaJeztah/docker,moul/docker,nawawi/docker,moul/docker,Mokolea/docker,moul/docker,nalind/docker,bearstech/moby,jimjag/docker,nawawi/docker,gnailuy/docker,gnailuy/docker,moby/moby,konstruktoid/docker-upstream,jimjag/docker,trebonian/docker,Mokolea/docker,gnailuy/docker,Ramzec/docker,jimjag/docker,Ramzec/docker,moby/moby,flavio/docker,flavio/docker,vdemeester/docker,bearstech/moby,nawawi/docker,mahak/docker,nalind/docker,Mokolea/docker,gnailuy/docker,trebonian/docker,trebonian/docker,thaJeztah/docker,konstruktoid/docker-upstream,vdemeester/docker