Update ruby-mixlib-shellout package to 3.1.6.
3.1.6 (2020-09-10)
* Use dir instead of FILE #220 (tas50)
* Simplify things a bit with &. #221 (tas50)
3.1.4 (2020-08-13)
* Fix a few typos #217 (tas50)
* Optimize requires for non-omnibus installs #218 (tas50)
3.1.2 (2020-07-24)
* convert helper to default_paths API #216 (lamont-granquist)
3.1.1 (2020-07-18)
3.1.0 (2020-07-17)
* shellout_spec: make "current user" independent of the environment #203
(terceiro)
* Minor doc fixes#205 (phiggins)
* extracting shell_out helper to mixlib-shellout #206 (lamont-granquist)
* Bumping minor version #207 (lamont-granquist)
* Test on Ruby 2.7 final, update chefstyle, and other CI fixes#208 (tas50)
* Bump minor for release #210 (lamont-granquist)
* Bumping minor for release again, again. #211 (lamont-granquist)
3be93f19ad