Readme includes dead mailing list link

[zrhoffman]

Steps to reproduce:

1. Open Readme

2. Navigate to mailing list link:

   servo-starters/README.md

   Line 27 in 4771c12

   You can also join the [`dev-servo` mailing list](https://lists.mozilla.org/listinfo/dev-servo).

Expected result: Visit dev-servo mailing list

Actual result: lists.mozilla.org does not resolve