Remove pry-stack-explorer test dep
Remove pry-stack-explorer test dep

We don't use this and it causes failures in Ruby 2.4 tests

Signed-off-by: Tim Smith <764ef62106582a09ed09dfa0b6bff7c05fd7d1e4@chef.io>

chef/mixlib-install,chef/mixlib-install,chef/mixlib-install