add all the .btn-purple selectors to deprecations.js

[shawnbot]

Deleting .btn-purple in #736 actually removes a bunch of other, more specific CSS selectors from the stats. In order to appease the deprecations test script introduced in #889, we need to add all of these to the selector deprecations list for 13.0.0. Running script/test-deprecations.js on this branch yields:

i 28 selectors removed locally (compared with latest)
i 28 selectors deprecated in v13.0.0
✓ ".btn-purple" is officially deprecated
✓ ".btn-purple:focus" is officially deprecated
✓ ".btn-purple.focus" is officially deprecated
✓ ".btn-purple:hover" is officially deprecated
✓ ".btn-purple.hover" is officially deprecated
✓ ".btn-purple:active" is officially deprecated
✓ ".btn-purple.selected" is officially deprecated
✓ "[open]>.btn-purple" is officially deprecated
✓ ".btn-purple:disabled" is officially deprecated
✓ ".btn-purple.disabled" is officially deprecated
✓ ".btn-purple .Counter" is officially deprecated
✓ ".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

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