json option no longer work with got.stream.post

[sylvaindumont]

Describe the bug

• Node.js version: 12.13.0
• OS & version: Ubuntu 19.10

got.stream.post no longer works with json option since #921

Actual behavior

a body is set in asStream
the request now have a body and a json option and throw in normalizeRequestArguments

Expected behavior

the json argument should work with got.stream.post, as it did until #921

Code to reproduce

got.stream.post('https://sindresorhus.com',  {json: {}})

Checklist

• I have read the documentation.
• I have tried my code with the latest version of Node.js and Got.

[szmarczak]

got/source/as-stream.ts

Line 22 in abdfee2

if (options.body) {

Should be options.body || options.json || options.form