Remove MobileUrlRewriter

[marcosholgado]

Task/Issue URL: https://app.asana.com/0/1125189844152671/1199921546480456
Tech Design URL:
CC:

Description:
This PR removes a redirect from facebook.com to the m. domain and reenables desktop mode for Facebook.

Steps to test this PR:

Redirect removed

1. Go to www.facebook.com
2. Since we are changing the user agent but we are not doing our own redirect anymore you should see the site loading a few times.

Other subdomains working

1. Login into Facebook
2. Search for Hero Wars (a game)
3. Click on Play Game
4. The game should load successfully.
5. If you try the same from develop you should see a Page not found error on Facebook.

Desktop mode

1. Go to Facebook.
2. In the overflow menu the Desktop Site checkbox should be enabled.
3. Click to enable desktop mode.
4. Site should successfully change to desktop mode.

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Internal references:

Software Engineering Expectations
Technical Design Template

[CDRussell]

Looks good.

FYI, on testing, I don't have a Facebook account to test against so couldn't verify logging in scenario.