all: enable GOEXPERIMENT=swissmap by default

all: enable GOEXPERIMENT=swissmap by default

For #54766.

Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-longtest,gotip-linux-amd64-longtest-race,gotip-linux-arm64-longtest,gotip-linux-386-longtest,gotip-darwin-amd64-longtest,gotip-darwin-arm64_13,gotip-linux-ppc64_power10,gotip-linux-arm
Change-Id: I5db0edcc156ed2e4bedc036b0baba2669e10c87a
Reviewed-on: https://go-review.googlesource.com/c/go/+/594597
Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>