fix(styles): replace old spacing variables with new ones

[jendowns]

I noticed there were a couple places where the old spacing variables were being used, so I replaced them with the new ones 👍

Based on the migration guide here: https://github.com/carbon-design-system/carbon/blob/master/docs/migration/10.x-layout.md#migrating

old variable	new variable
$spacing-3xs	$carbon--spacing-01, $spacing-01
$spacing-2xs	$carbon--spacing-02, $spacing-02
$spacing-xs	$carbon--spacing-03, $spacing-03
$spacing-sm	$carbon--spacing-04, $spacing-04
$spacing-md	$carbon--spacing-05, $spacing-05
$spacing-lg	$carbon--spacing-06, $spacing-06
$spacing-xl	$carbon--spacing-07, $spacing-07
$spacing-2xl	$carbon--spacing-08, $spacing-08
$spacing-3xl	$carbon--spacing-09, $spacing-09

Changelog

Changed

• replace old spacing variables with new syntax

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[joshblack]

Note to design review, these are the components that had their spacing tokens updated. Visually they should be the same unless the token used in the past was a mistake 👍

• Accordion
• Code Snippet
• Copy Button
• Data Table Action
• Pagination