Fix docs (or impl) of request_

[pepeiborra]

The docs say it's the same as sendRequest, which is non-blocking, but the implementation uses request, which blocks:

https://github.com/bubba/lsp-test/blob/23b1dcf20f37869d29158ebc38402503894bcd80/src/Language/Haskell/LSP/Test.hs#L267-L269

[lukel97]

That should probably say the same as 'request', will fix