Fix billy in README.md

Whoops #391 (comment)

cc @Billy-

Author: Kent C. Dodds

README.md

@@ -109,7 +109,7 @@ Thanks goes to these wonderful people ([emoji key](https://allcontributors.org/d
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     <td align="center"><a href="https://numb86.net/"><img src="https://avatars1.githubusercontent.com/u/16703337?v=4" width="100px;" alt=""/><br /><sub><b>numb86</b></sub></a><br /><a href="https://github.com/testing-library/testing-library-docs/commits?author=numb86" title="Documentation">📖</a></td>
     <td align="center"><a href="https://github.com/NicholasBoll"><img src="https://avatars2.githubusercontent.com/u/338257?v=4" width="100px;" alt=""/><br /><sub><b>Nicholas Boll</b></sub></a><br /><a href="https://github.com/testing-library/testing-library-docs/commits?author=NicholasBoll" title="Documentation">📖</a></td>
-    <td align="center"><a href="https://github.com/billy"><img src="https://avatars2.githubusercontent.com/u/48111?v=4" width="100px;" alt=""/><br /><sub><b>Billy</b></sub></a><br /><a href="#talk-Billy" title="Talks">📢</a> <a href="https://github.com/testing-library/testing-library-docs/commits?author=Billy" title="Documentation">📖</a></td>
+    <td align="center"><a href="https://github.com/Billy-"><img src="https://avatars2.githubusercontent.com/u/4316168?v=4" width="100px;" alt=""/><br /><sub><b>Billy Mathews</b></sub></a><br /><a href="#talk-Billy-" title="Talks">📢</a> <a href="https://github.com/testing-library/testing-library-docs/commits?author=Billy-" title="Documentation">📖</a></td>
   </tr>
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