Fix type loader when type check output overflows the buffer

[ojgarcia]

When running the parlour CLI and you have a large amount of sorbet typecheck errors,
the parlour process will hang.

Parlour::TypeLoader uses Open3.capture3 which comes with this warning

Take care to avoid deadlocks. Output streams stdout and stderr have fixed-size buffers, so reading extensively from one but not the other can cause a deadlock when the unread buffer fills. To avoid that, stdout and stderr should be read simultaneously (using threads or IO.select).

-- https://ruby-doc.org/3.4.1/stdlibs/open3/Open3.html#method-c-popen3

The code that calls Open3.capture3 only reads from stdout. So instead of implementing a fix for this, I switched to using Open3.capture2. Which returns stdout as a string and a Process::Status object.

This change should not affect the functionality of the CLI.