owners: add andybons and rakoczy as primaries for playground
owners: add andybons and rakoczy as primaries for playground

Change-Id: I1927873a2008097440c9dfd7263106b5af0abdf3
Reviewed-on: https://go-review.googlesource.com/c/build/+/234477
Run-TryBot: Andrew Bonventre <682ad9f487f614f19e8b7cc5d340bdc8e1c1b128@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Carlos Amedee <ab5e2bca84933118bbc9d48ffaccce3bac4eeb64@golang.org>

golang/build,golang/build,golang/build,golang/build