"background window" link on Declare Permissions page is obsolete. #840

Describe the bug
The description for the "background" permission on the Declare Permissions page links to developers.google.com/chrome/apps/docs/background.html, which in turn redirects to docs/apps/manifest/. The final page does not contain any relevant information about the background permission.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://developer.chrome.com/docs/extensions/mv3/declare_permissions/
2. Search for "background"
3. Click the last link the permission's description.
4. Look for any information on the background permission on the next page

Expected behavior
The linked page should provide a clear and concise description of the background permission.

Screenshots

Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Additional context

• The original link points to http://developers.google.com/chrome/apps/docs/background.html
• 307 redirects to https://developers.google.com/chrome/apps/docs/background.html
• 301 redirects to https://developers.google.com/chrome/apps/docs/background.html
• 307 redirects to http://developer.chrome.com/apps
• 301 redirects to https://developer.chrome.com/apps
• 301 redirects to https://developer.chrome.com/docs/apps/manifest
• 301 redirects to https://developer.chrome.com/docs/apps/manifest/

We can cut out a lot of these unnecessary hops by updating the link in /docs/extensions/mv3/declare_permissions/