runtime/coverage: remove refs to deprecated io/ioutil
Change-Id: I66965e6a61cf1726db06670978a4654b84f3fd72
GitHub-Last-Rev:
90023e48435029c94a316413b30e46c9ce0019d5
GitHub-Pull-Request: golang/go#65900
Reviewed-on: https://go-review.googlesource.com/c/go/+/566356
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Jorropo <jorropo.pgm@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>