vendor: update all dependencies

* Update all dependencies
  * Remove all `[[constraint]]` from Gopkg.toml
  * Add in the minimum number of `[[override]]` to build
  * Remove go get of github.com/inconshreveable/mousetrap as it is vendored
  * Update docs with new policy on constraints

vendor/google.golang.org/api/transport/grpc/go18.go

@@ -22,5 +22,5 @@ import (
 )
 
 func addOCStatsHandler(opts []grpc.DialOption) []grpc.DialOption {
-	return append(opts, grpc.WithStatsHandler(&ocgrpc.ClientHandler{NoStats: true}))
+	return append(opts, grpc.WithStatsHandler(&ocgrpc.ClientHandler{}))
 }