Update styling of reduced nav on small screens

[bartaz]

Done

Updates the styling of top reduced navigation on mobile screens to match desktop:

• changes background to alternative
• changes text colour (and icons) to muted

Fixes https://warthogs.atlassian.net/browse/WD-13652

QA

• Open demo
• Check the very top navigation bar (the one that says Canonical) on mobile screen
• Make sure that the background and text colour is the same as on large screen (not the same as navigation below it)

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 release (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.

Screenshots

[webteam-app]

Demo

Jenkins

demos.haus

[lyubomir-popov]

much better! two final things:

• the weight of "Canonical Ubuntu" is 300 instead of 400, like the links on the right. It should match so 400
  
• the mobile nav threshold var might need an adjustment as things wrap:
  

[petesfrench]

does the X use to close the search need to be the same colour as the other items?

Apart from that, LGTM

[bartaz]

does the X use to close the search need to be the same colour as the other items?

Yes, as far as I understand, the X is when the search is "Selected" so we show it in standard text colour, not muted.

[lyubomir-popov]

colours look good, but I would make the small caps headings muted. they also feel a little too bold - but that could be due to the background color

[petesfrench]

LGTM