Test not launching on macOS 11.2 / Chrome 89

I have a fresh checkout and tests fail to launch with these errors:

```
Mar  5 18:42:32  Google Chrome Helper[56315] <Error>: SeatbeltExecServer: Failed to initialize sandbox: -1 Operation not permitted
[0305/184232.531717:ERROR:network_service_instance_impl.cc(286)] Network service crashed, restarting service.
```