Multiline Context Manager 'with/as' parsing error

[jacobian91]

Describe the bug
Black reports a parsing error when using multiline context managers using the 'with/as' pattern.

To Reproduce
Run the below code for the parsing issue. Then remove as x as y as z, this will run without issue.

with (
    open("xxxxxxxxxxxxxxxxxxxx", "w") as x,
    open("yyyyyyyyyyyyyyyyyyyyyy", "w") as y,
    open("zzzzzzzzzzzzzzzzzzz", "w") as z,
):
    x.write("x")
    y.write("y")
    z.write("z")

Expected behavior
No error, this is valid code that runs on python 3.9

Environment

• Version: main
• Windows Python 3.9.1

Does this bug also happen on main? To answer this, you have two options:
Yes, using https://black.vercel.app/?version=main

[JelleZijlstra]

See #1948.