README.md: fix GoDoc badge source Change-Id: If0bb1f30b604709c650e3d7b08d90a00dcbcead1

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