README,libct/README: fix pkg.go.dev badges

What used to be godoc.org is now pkg.go.dev, and while the old URLs
still work, they might be broken in the future.

Updated badges are generated via https://pkg.go.dev/badge/

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit f309a69)
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

README.md

@@ -1,7 +1,7 @@
 # runc
 
 [![Go Report Card](https://goreportcard.com/badge/github.com/opencontainers/runc)](https://goreportcard.com/report/github.com/opencontainers/runc)
-[![GoDoc](https://godoc.org/github.com/opencontainers/runc?status.svg)](https://godoc.org/github.com/opencontainers/runc)
+[![Go Reference](https://pkg.go.dev/badge/github.com/opencontainers/runc.svg)](https://pkg.go.dev/github.com/opencontainers/runc)
 [![CII Best Practices](https://bestpractices.coreinfrastructure.org/projects/588/badge)](https://bestpractices.coreinfrastructure.org/projects/588)
 [![gha/validate](https://github.com/opencontainers/runc/workflows/validate/badge.svg)](https://github.com/opencontainers/runc/actions?query=workflow%3Avalidate)
 [![gha/ci](https://github.com/opencontainers/runc/workflows/ci/badge.svg)](https://github.com/opencontainers/runc/actions?query=workflow%3Aci)

libcontainer/README.md

@@ -1,6 +1,6 @@
 # libcontainer
 
-[![GoDoc](https://godoc.org/github.com/opencontainers/runc/libcontainer?status.svg)](https://godoc.org/github.com/opencontainers/runc/libcontainer)
+[![Go Reference](https://pkg.go.dev/badge/github.com/opencontainers/runc/libcontainer.svg)](https://pkg.go.dev/github.com/opencontainers/runc/libcontainer)
 
 Libcontainer provides a native Go implementation for creating containers
 with namespaces, cgroups, capabilities, and filesystem access controls.