runtime: use Escape instead of escape in export_test.go
runtime: use Escape instead of escape in export_test.go

I landed the bottom CL of my stack without rebasing or retrying trybots,
but in the rebase "escape" was removed in favor of "Escape."

Change-Id: Icdc4d8de8b6ebc782215f2836cd191377cc211df
Reviewed-on: https://go-review.googlesource.com/c/go/+/403755
Reviewed-by: Bryan Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>
Run-TryBot: Michael Knyszek <4473450dc5c88f06e1fb787f303d7805ec2aee65@google.com>

golang/go,golang/go,golang/go,nawawi/go,nawawi/go,golang/go,nawawi/go,golang/go,nawawi/go,golang/go,nawawi/go,golang/go,nawawi/go,golang/go,nawawi/go,nawawi/go