container/heap: call t.Helper() in verify()
container/heap: call t.Helper() in verify()

I modified verify() to fail every time to test the change. Before adding
t.Helper() (line 37 is in verify()):
/.../go/src/container/heap/heap_test.go:37: forced failure
FAIL

Afer adding t.Helper() (line 67 is where verify() is called):
/.../go/src/container/heap/heap_test.go:67: forced failure
FAIL

Fixes #21863

Change-Id: I46f0c8ec413cc664358c568fc53e48bb4a1d03d0
Reviewed-on: https://go-review.googlesource.com/63570
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
Run-TryBot: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

akutz/go,josharian/go,akutz/go,josharian/go,golang/go,christopher-henderson/Go,polyverse-security/go,akutz/go,CAFxX/go,golang/go,polyverse-security/go,josharian/go,cloudflare/go,Cofyc/go,codestation/go,polyverse-security/go,CAFxX/go,nawawi/go,polyverse-security/go,cloudflare/go,Cofyc/go,Cofyc/go,akutz/go,codestation/go,codestation/go,josharian/go,golang/go,josharian/go,golang/go,golang/go,cloudflare/go,cloudflare/go,polyverse-security/go,cloudflare/go,codestation/go,akutz/go,CAFxX/go,cloudflare/go,cloudflare/go,akutz/go,CAFxX/go,josharian/go,Cofyc/go,codestation/go,nawawi/go,codestation/go,akutz/go,nawawi/go,nawawi/go,nawawi/go,josharian/go,golang/go,Cofyc/go,codestation/go,CAFxX/go,nawawi/go,nawawi/go,CAFxX/go,CAFxX/go,polyverse-security/go,polyverse-security/go,Cofyc/go,codestation/go,golang/go,akutz/go,nawawi/go,josharian/go,golang/go,cloudflare/go,Cofyc/go,CAFxX/go,Cofyc/go,polyverse-security/go