Bump actions/cache from 2.1.5 to 2.1.6 (#161)

Bumps [actions/cache](https://github.com/actions/cache) from 2.1.5 to 2.1.6. - [Release notes](https://github.com/actions/cache/releases) - [Commits](actions/cache@v2.1.5...v2.1.6) Signed-off-by: dependabot[bot] <[email protected]> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]