docs: update the Udash versions used by the documentation examples - #3749

Changed pages include:

• index.html - view
• 404.html - view
• blog/index.html - view
• changelogs/index.html - view
• code-of-conduct/index.html - view
• contact/index.html - view
• contributors/index.html - view
• docs/index.html - view
• plugins/index.html - view
• privacy-policy/index.html - view

There are more changes not included in the list