Remove Kokkos due to multiple conflicts

packages/kokkos/.clang-format

packages/kokkos/.clang-format-ignore

packages/kokkos/.clang-tidy

packages/kokkos/.codecov.yml

packages/kokkos/.gitignore

packages/kokkos/.gitrepo

packages/kokkos/.jenkins

packages/kokkos/.travis.yml

packages/kokkos/BUILD.md

packages/kokkos/CHANGELOG.md

packages/kokkos/CMakeLists.txt

packages/kokkos/CONTRIBUTING.md

packages/kokkos/Copyright.txt

packages/kokkos/HOW_TO_SNAPSHOT

packages/kokkos/LICENSE

packages/kokkos/Makefile.kokkos

packages/kokkos/Makefile.targets

packages/kokkos/README.md

packages/kokkos/Spack.md

packages/kokkos/algorithms/CMakeLists.txt