os: deflake TestFdReadRace by increasing timeout
os: deflake TestFdReadRace by increasing timeout

This timeout will never be reached if the test passes, so it doesn't
much matter how long it is. The test is t.Parallel so on a slow system
1 second may occasionally not be enough, although on my laptop the
test takes about 0.02 seconds.

Fixes #34431

Change-Id: Ia2184e6be3747933bfe83aa6c8e1f77e6b1e0bba
Reviewed-on: https://go-review.googlesource.com/c/go/+/200764
Run-TryBot: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
Reviewed-by: Bryan C. Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>

CAFxX/go,nawawi/go,golang/go,cloudflare/go,nawawi/go,golang/go,cloudflare/go,nawawi/go,akutz/go,cloudflare/go,golang/go,CAFxX/go,akutz/go,CAFxX/go,CAFxX/go,nawawi/go,akutz/go,cloudflare/go,nawawi/go,CAFxX/go,cloudflare/go,CAFxX/go,akutz/go,CAFxX/go,akutz/go,golang/go,golang/go,CAFxX/go,akutz/go,akutz/go,cloudflare/go,nawawi/go,golang/go,akutz/go,cloudflare/go,golang/go,nawawi/go,cloudflare/go,golang/go,nawawi/go