net: add even more timing slop for TestDialParallel
This test expects dials of a closed port to complete in about the same
amount of time: an initial probe value +/- 20%. Reduce test flakes on
Windows by increasing the slop to +/- 50% of the original value.
Fixes #52173
Change-Id: I813492c36aca2b0264b3b5b8c96e8bf97193af76
Reviewed-on: https://go-review.googlesource.com/c/go/+/408354
Run-TryBot: Damien Neil <dneil@google.com> Reviewed-by: Bryan Mills <bcmills@google.com> Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>