runtime: disable test for 78081

The stack we're trying to revert for this issue is tripping
on the test for it. The test fails halfway through the revert stack.
Disable it for now, we can re-enable once the whole revert stack is in.

Change-Id: I3bc2d2f069030d865f799a63ad0f267aa667db07
Reviewed-on: https://go-review.googlesource.com/c/go/+/757224
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

test/fixedbugs/issue78081.go

@@ -9,6 +9,10 @@ package main
 import "runtime"
 
 func main() {
+	if true {
+		// Disabled until CL 757343 is in.
+		return
+	}
 	runtime.GOMAXPROCS(2)
 	c := make(chan bool)
 	for i := 0; i < 16; i++ {