Fixes broken redirect from the Workbox "Getting Started" guide.

[malchata]

What's changed, or what was fixed?

• A redirect for the "Getting Started" guide for Workbox was not redirected, resulting in a 404. This was fixed.

Fixes: GoogleChrome/workbox#3085

Target Live Date: 2022-05-31

• [ ] This has been reviewed and approved by (@jeffposnick).
• [x] I have run npm test locally and all tests pass (@malchata).
• [ ] I have added the appropriate type-something label (@jeffposnick).
• [x] I've staged the site and manually verified that my content displays correctly (@malchata).

CC: @jeffposnick