Removing deprecated column grid styles

[jonrohan]

This removes all the deprecated column grid styles.

• .container
• .column, .columns
• one-half, etc...

@shawnbot

ref https://github.com/github/design-systems/issues/59

[shawnbot]

Ah, @jonrohan it looks like the test failed because this removes the /objects/layout from the docs. You'll need to explicitly mark this as removed as in this change:

  '/objects/layout': removed,

[jonrohan]

We're gonna push this PR for v12. Instead we're adding a warning #663

[shawnbot]

FYI, I'm queueing this up for inclusion in #887 (v13.0.0). 🎉

[vercel]

This pull request is automatically deployed with Now.
To access deployments, click Details below or on the icon next to each push.

Latest deployment for this branch: https://primer-css-git-removecolumnstyles.primer.now.sh

[shawnbot]

As of 40bca3c, running the deprecations test script (see #889) yields:

script/test-deprecations.js
i 17 selectors removed locally (compared with latest)
i 18 selectors deprecated in v13.0.0
𐄂 ".btn-purple" deprecated, but not removed
✓ ".text-pending" is officially deprecated
✓ ".bg-pending" is officially deprecated
✓ ".container" is officially deprecated
✓ ".container::before" is officially deprecated
✓ ".container::after" is officially deprecated
✓ ".columns" is officially deprecated
✓ ".columns::before" is officially deprecated
✓ ".columns::after" is officially deprecated
✓ ".column" is officially deprecated
✓ ".one-third" is officially deprecated
✓ ".two-thirds" is officially deprecated
✓ ".one-fourth" is officially deprecated
✓ ".one-half" is officially deprecated
✓ ".three-fourths" is officially deprecated
✓ ".one-fifth" is officially deprecated
✓ ".four-fifths" is officially deprecated
✓ ".centered" is officially deprecated

I had to explicitly add ::before and ::after selectors to the deprecations list, but I wonder if it makes sense to ignore those if the "parent" selector (in this case, .container and .columns) is being deprecated? Or maybe it's just better to be explicit? 🤷‍♀

[shawnbot]

Let's do this!