Revert "runtime: convert local var stop,ready at TestDebugCallUnsafePoint to atomic...

Revert "runtime: convert local var stop,ready at TestDebugCallUnsafePoint to atomic type"

This reverts https://go.dev/cl/427135.

Reason for revert: broke the test it modified on linux-amd64-noopt.

    --- FAIL: TestDebugCallUnsafePoint (0.00s)
        debug_test.go:265: want "call not at safe point", got %!s(<nil>)

Change-Id: I044c9720aed2d5e48b56bd7ab2781462270dcae9
Reviewed-on: https://go-review.googlesource.com/c/go/+/428395
Reviewed-by: xie cui <523516579@qq.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: hopehook <hopehook@golangcn.org>
Reviewed-by: Michael Pratt <mpratt@google.com>