Update Michael Rebello's employment (#229)

Update to reflect @rebello95's current employment.

Author: akshayjshah

MAINTAINERS.md

@@ -3,7 +3,7 @@ Maintainers
 
 ## Current
 * [Peter Edge](https://github.com/bufdev), [Buf](https://buf.build)
-* [Michael Rebello](https://github.com/rebello95), [Buf](https://buf.build)
+* [Michael Rebello](https://github.com/rebello95), [Airbnb](https://airbnb.com)
 * [Philip Warren](https://github.com/pkwarren), [Buf](https://buf.build)
 * [Josh Humphries](https://github.com/jhump), [Buf](https://buf.build)