chore(tag): update design

[dancormier]

STACKS-459

This PR updates the design of the tag component.

To test

1. Go to the Tag page on the Deploy Preview
2. Verify that tags render as expected
   • Note: Use the mode switcher in the topbar menu to check different combinations of light/dark/high-contrast
3. Optional: Check out the Post Summary page on the Deploy Preview to ensure tags render as expected in this context

It includes

• Updated styles for the default, moderator, and required tags
• Removal of the muted variant
• Removal of the is-selected modifier

It does not include

• Any "Teams" tag styles (those are handled in Core with --theme-tag-* CSS variables)
• Any changes to the post summary component
  • Opacity-related fixes
  • Dark mode yellow background color

Follow up integration tasks

We'll need to make a few updates to Core to ensure things render as expects. These include:

• Update styles of the .post-tag class to match updated .s-tag styles
• Removal of any --theme-tag-* variables from SE themes (I think. We'll need to at least check to see if this is necessary)
• Update Team tag colors to match expectations

Screenshot comparisons

Variant	Before	After
default
moderator
required

---

cc @ellenchanhy (I'm cc-ing you here but if you'd like to be an "official" reviewer, you can ask helpdesk to be included in the StackExchange team. Once that's done, I can add you to the Stacks repo as a contributor)

[netlify[bot]]

✅ Deploy Preview for stacks ready!

Name	Link
🔨 Latest commit	5fe23be76a9b970bdbfb34a6210203d8c438bdfd
🔍 Latest deploy log	https://app.netlify.com/sites/stacks/deploys/662f79634828a100082cf657
😎 Deploy Preview	https://deploy-preview-1717--stacks.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.