Update accordion

[andesol]

Done

• Update accordion styling, according to Accordion update - build #4397

Fixes #4397

QA

• Open demo
• Find the accordion in the examples section an check it matches the design
  e.g. https://vanilla-framework-4406.demos.haus/docs/examples/patterns/accordion/default

Check if PR is ready for release

If this PR contains Vanilla SCSS code changes, it should contain the following changes to make sure it's ready for the release:

• PR should have one of the following labels to automatically categorise it in release notes:
  • Feature 🎁, Breaking Change 💣, Bug 🐛, Documentation 📝, Maintenance 🔨.
• Vanilla version in package.json should be updated relative to the most recent release, following semver convention:
  • if CSS class names are not changed it can be bugfix relesase (x.x.X)
  • if CSS class names are changed/added/removed it should be minor version (x.X.0)
  • see the wiki for more details
• Any changes to component class names (new patterns, variants, removed or added features) should be listed on the what's new page.
• Documentation side navigation should be updated with the relevant labels.

[webteam-app]

Demo starting at https://vanilla-framework-4406.demos.haus

[bartaz]

Something happened to the borders between accordion items, they are not visible until accordion is open (?).
It seems to be related to position: relative added to the button, but I haven't figured out yet how to get around that:

[bartaz]

@andesol I guess we should bump the version to 3.2.1 in this one. And while it is not a new "feature" from CSS point of view, the design change is quite important and visible, so would be good to add Accordion as "Updated" in side nav and in "what's new page".

[bartaz]

LGTM

[lyubomir-popov]

LGTM