internal/poll: remove alloc sending IPv6 UDP on Windows
internal/poll: remove alloc sending IPv6 UDP on Windows

This was an oversight in CL 331511.

Change-Id: Ibc20bf6ea80a8675d43d9691ed551dffab1d9215
Reviewed-on: https://go-review.googlesource.com/c/go/+/361254
Trust: Josh Bleecher Snyder <cdc248cc4d32e4fbfe04e45228163bcecd48a0b9@gmail.com>
Trust: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
Run-TryBot: Josh Bleecher Snyder <cdc248cc4d32e4fbfe04e45228163bcecd48a0b9@gmail.com>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

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