chore: update GoDoc badge to pkg.go.dev
# Google Cloud Client Libraries for Go
-[![GoDoc](https://godoc.org/cloud.google.com/go?status.svg)](https://pkg.go.dev/cloud.google.com/go)
+[![Go Reference](https://pkg.go.dev/badge/cloud.google.com/go.svg)](https://pkg.go.dev/cloud.google.com/go)
Go packages for [Google Cloud Platform](https://cloud.google.com) services.
