build: go mod tidy (#3451)

tidy up a bit; go build also made changs to go.mod, meaning this would
have been (again) a dirty release.

Need some better automation for this crap.
Signed-off-by: Miek Gieben <miek@miek.nl>

go.mod

@@ -44,7 +44,6 @@ require (
 	golang.org/x/net v0.0.0-20191003171128-d98b1b443823 // indirect
 	golang.org/x/sys v0.0.0-20191010194322-b09406accb47
 	google.golang.org/api v0.13.0
-	google.golang.org/genproto v0.0.0-20190701230453-710ae3a149df // indirect
 	google.golang.org/grpc v1.25.1
 	gopkg.in/DataDog/dd-trace-go.v1 v1.19.0
 	gopkg.in/inf.v0 v0.9.1 // indirect