runtime: relax TestWindowsStackMemory from 100kB to 128kB

We've been getting intermittent flakes in this test since 2023,
all reporting values just barely over 100kB on windows-386.

If we were happy with 100kB, we should be happy with 128kB,
and it should fix the flakes.

Fixes #58570.

Change-Id: Iabe734cfbba6fe28a83f62e7811ee03fed424f0b
Reviewed-on: https://go-review.googlesource.com/c/go/+/628795
LUCI-TryBot-Result: Go LUCI <[email protected]>
Auto-Submit: Russ Cox <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>

Author: rsc

src/runtime/syscall_windows_test.go

@@ -673,7 +673,7 @@ func TestWindowsStackMemory(t *testing.T) {
 	if err != nil {
 		t.Fatalf("Failed to read stack usage: %v", err)
 	}
-	if expected, got := 100<<10, stackUsage; got > expected {
+	if expected, got := 128<<10, stackUsage; got > expected {
 		t.Fatalf("expected < %d bytes of memory per thread, got %d", expected, got)
 	}
 }