build.sh: remove 2.1 so we can merge to master without breaking CI
build.sh: remove 2.1 so we can merge to master without breaking CI

omajid/s2i-dotnetcore,omajid/s2i-dotnetcore,redhat-developer/s2i-dotnetcore,redhat-developer/s2i-dotnetcore,omajid/s2i-dotnetcore,redhat-developer/s2i-dotnetcore