SignalR Karma test issues warning about deprecated API

As of the change at https://github.com/dotnet/aspnetcore/pull/36802, the `run-tests.ts` code logs the following warning:

```
WARN [karma-server]: Passing raw CLI options to new Server(config, done) is deprecated. Use parseConfig(configFilePath, cliOptions, {promiseConfig: true, throwErrors: true}) to prepare a processed Config instance and pass that as the config argument instead.
```

This refers to the code at https://github.com/dotnet/aspnetcore/blob/302cfd93d8ff643662c0f8f4690b09cd7408d1d3/src/SignalR/clients/ts/FunctionalTests/scripts/run-tests.ts#L212

Although this doesn't cause any build or test failures, it suggests that at some point, Karma is going to remove this API and the code will stop working.