internal,runtime: use the builtin clear
To simplify the code.
Change-Id: I023de705504c0b580718eec3c7c563b6cf2c8184
GitHub-Last-Rev:
026b32c799b13d0c7ded54f2e61429e6c5ed0aa8
GitHub-Pull-Request: golang/go#73412
Reviewed-on: https://go-review.googlesource.com/c/go/+/666118
Reviewed-by: Keith Randall <khr@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: Michael Pratt <mpratt@google.com>