[WALL-2135]{BpkAccordion] Fix accordion wothout divider

[ss-tombrown]

• This PR fixes an issue introduced via this PR that stopped the divider prop from working.
• Adds a story/example of Accordion without divider on dark.

Before

After

Remember to include the following changes:

• [x] Ensure the PR title includes the name of the component you are changing so it's clear in the release notes for consumers of the changes in the version e.g [KOA-123][BpkButton] Updating the colour
• [ ] README.md (If you have created a new component)
• [ ] Component README.md
• [ ] Tests
• [ ] Accessibility tests
  • The following checks were performed:
    • [ ] Ability to navigate using a keyboard only
    • [ ] Zoom functionality (Deque University explanation):
      • [ ] The page SHOULD be functional AND readable when only the text is magnified to 200% of its initial size
      • [ ] Pages must reflow as zoom increases up to 400% so that content continues to be presented in only one column i.e. Content MUST NOT require scrolling in two directions (both vertically and horizontally)
    • [ ] Ability to navigate using a screen reader only
• [ ] Storybook examples created/updated
• [ ] For breaking changes or deprecating components/properties, migration guides added to the description of the PR. If the guide has large changes, consider creating a new Markdown page inside the component's docs folder and link it here

[github-actions[bot]]

Visit https://backpack.github.io/storybook-prs/3559 to see this build running in a browser.

[github-actions[bot]]

Visit https://backpack.github.io/storybook-prs/3559 to see this build running in a browser.

[github-actions[bot]]

Browser support

If this is a visual change, make sure you've tested it in multiple browsers.

Generated by :no_entry_sign: dangerJS against 23272233b0b679a76d75f6d30c974f861abe7b24