Test instability when launching a new process within a test.

### What happened?

As noted in https://github.com/Azure/data-api-builder/pull/1402/commits/a7ae343e0a9c3616ed328579aadbadb45fffe8ef we have a test that is not stable across OSes (it worked on Windows but not Linux).

There seems to be something problematic when it comes to how we launch a new process within a test and then capture the output of it to then test against.

We should review if this method we're using is the best way in which we can launch a process within a test, and if it's the best way to read the `stdout` and `stderr` streams.