Update APIs to use new Google cloud paths.

grpc/discovery/internal/testservices/pb.discovery.go

 // AUTOGENERATED. DO NOT EDIT.
 
 package testservices
 
 import discovery "github.com/luci/luci-go/grpc/discovery"
 
-import "github.com/luci/luci-go/common/proto/google/descriptor"
+import "google.golang.org/genproto/protobuf"
 
 func init() {
         discovery.RegisterDescriptorSetCompressed(
                 []string{
                         "testservices.Greeter", "testservices.Calc",
                 },
                 []byte{31, 139,
                         8, 0, 0, 9, 110, 136, 0, 255, 116, 148, 209, 110, 227, 68,
                         20, 134, 61, 227, 137, 235, 156, 186, 141, 119, 72, 150, 196, 106,
                         210, 169, 145, 88, 132, 88, 103, 27, 4, 23, 32, 144, 74, 181,
@@ skipping 62 matching lines @@
 //
 // Do NOT modify the returned descriptor.
 func FileDescriptorSet() *descriptor.FileDescriptorSet {
         // We just need ONE of the service names to look up the FileDescriptorSet.
         ret, err := discovery.GetDescriptorSet("testservices.Greeter")
         if err != nil {
                 panic(err)
         }
         return ret
 }