runtime/race: be less picky about test run time

Currently, there are two regexps in the race detector output tests
that assume subtests will complete in < 1 second. This isn't necessary
and very occasionally fails (on builders that are probably very
loaded). Make these tests less picky about timing.

Fixes #50612.

Change-Id: Ib3f94d6c5dc37541dbeb06de71cf462a74af844b
Reviewed-on: https://go-review.googlesource.com/c/go/+/378581


Trust: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>