Fix design/accessibility redirects on primer.style

[rezrah]

• Closes https://github.com/github/primer/issues/1707

2nd attempt. Fixes URL redirects by moving them above the rewrites, which were taking precedent.

Now all urls that went to primer.style/design/accessibility/* go to primer.style/design/guides/accessibility/*

Fixed and tested on staging site:

https://primerstyle-staging.azurewebsites.net/design/accessibility https://primerstyle-staging.azurewebsites.net/design/accessibility/tooltip-alternatives

☝️ These links would normally 404, but now will redirect correctly.

[emilybrick]

✨ thank you for doing this so quickly!