build(deps): bump ruby in /.circleci/rspec-runner
build(deps): bump ruby in /.circleci/rspec-runner

Bumps ruby from 2.6.3-slim-buster to 2.6.4-slim-buster.

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
minimum2scp/dockerfiles,minimum2scp/dockerfiles,minimum2scp/dockerfiles