Go 1.21

[AkihiroSuda]

gvisor-tap-vsock is updated too to fix the following compilation failure

package github.com/lima-vm/lima/cmd/limactl
	imports github.com/lima-vm/lima/pkg/hostagent
	imports github.com/lima-vm/lima/pkg/driverutil
	imports github.com/lima-vm/lima/pkg/qemu
	imports github.com/lima-vm/lima/pkg/networks/usernet
	imports github.com/containers/gvisor-tap-vsock/pkg/virtualnetwork
	imports github.com/containers/gvisor-tap-vsock/pkg/services/dhcp
	imports github.com/containers/gvisor-tap-vsock/pkg/tap
	imports gvisor.dev/gvisor/pkg/tcpip/stack
	imports gvisor.dev/gvisor/pkg/sync/locking
	imports gvisor.dev/gvisor/pkg/gohacks: build constraints exclude all Go files in /home/runner/go/pkg/mod/gvisor.dev/[email protected][121](https://github.com/lima-vm/lima/actions/runs/5833420145/job/15820839995?pr=1729#step:4:122)6231429-a78e892a26d2/pkg/gohacks