x/playground: builds failing on misc-compile-linux-loong64 and misc-compile-freebsd-riscv64-go1.20 builders

[findleyr]

In https://go.dev/cl/467955, we see that the misc-compile-linux-loong64 and misc-compile-freebsd-riscv64-go1.20 are failing with errors related to the x/sys dependency.

It looks like the dependencies of x/playground are quite old, and x/sys needs to be updated. Surprisingly, x/playground is not included in build.golang.org.

[gopherbot]

Change https://go.dev/cl/478959 mentions this issue: all: update golang.org/x/ dependencies