testing: incorrect comment about max number of simultaneous goroutines running with -race flag

[pkositsyn]

What version of Go are you using (go version)?

go version go1.16 darwin/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output

GOOS="darwin"
GOARCH="amd64"

What did you do?

Run a program with -race flag exceeding max number of goroutines

What did you expect to see?

Expected to see a limit of 8192 as pointed out here

go/src/testing/testing.go

Line 193 in dc289d3

// The race detector kills the program if it exceeds 8192 concurrent goroutines,

What did you see instead?

race: limit on 8128 simultaneously alive goroutines is exceeded, dying

I don't know whether this number is system-specific or not, but it is exactly 8128 for darwin/amd64 and linux/arm64 at least.

[gopherbot]

Change https://golang.org/cl/304254 mentions this issue: testing: update permitted number of -race goroutines