fix(docs): Fix version number in CDN link being malformatted - #5802

Done

Changes formatting of the Vanilla URL in CDN links to use dots inside the version number instead of underscores

Fixes #5793
Fixes https://warthogs.atlassian.net/browse/WD-36205
Fixes https://chat.canonical.com/canonical/pl/dwo4wuwarib3dm86bjxuik11pw

QA

• Open demo
• Open the getting started page
• Verify the CDN url (when the version is replaced with 4.50.0 instead of 4.51.0) does not 404

Check if PR is ready for release

If this PR contains Vanilla SCSS or macro 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 existing APIs (CSS classes & macro APIs) are not changed it can be a bugfix release (x.x.X)
  • if existing APIs (CSS classes & macro APIs) are changed/added/removed it should be a minor version (x.X.0)
  • see the wiki for more details
• Any changes to component class names (new patterns, variants, removed or added features) or macros should be listed on the what's new page.