build(deps): Bump google.golang.org/grpc from 1.30.0 to 1.31.0

Bumps [google.golang.org/grpc](https://github.com/grpc/grpc-go) from 1.30.0 to 1.31.0.
- [Release notes](https://github.com/grpc/grpc-go/releases)
- [Commits](https://github.com/grpc/grpc-go/compare/v1.30.0...v1.31.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

go.mod

@@ -30,5 +30,5 @@ require (
 	github.com/tendermint/tm-db v0.6.0
 	golang.org/x/crypto v0.0.0-20200406173513-056763e48d71
 	golang.org/x/net v0.0.0-20200324143707-d3edc9973b7e
-	google.golang.org/grpc v1.30.0
+	google.golang.org/grpc v1.31.0
 )

go.sum

@@ -648,6 +648,8 @@ google.golang.org/grpc v1.26.0 h1:2dTRdpdFEEhJYQD8EMLB61nnrzSCTbG38PhqdhvOltg=
 google.golang.org/grpc v1.26.0/go.mod h1:qbnxyOmOxrQa7FizSgH+ReBfzJrCY1pSN7KXBS8abTk=
 google.golang.org/grpc v1.30.0 h1:M5a8xTlYTxwMn5ZFkwhRabsygDY5G8TYLyQDBxJNAxE=
 google.golang.org/grpc v1.30.0/go.mod h1:N36X2cJ7JwdamYAgDz+s+rVMFjt3numwzf/HckM8pak=
+google.golang.org/grpc v1.31.0 h1:T7P4R73V3SSDPhH7WW7ATbfViLtmamH0DKrP3f9AuDI=
+google.golang.org/grpc v1.31.0/go.mod h1:N36X2cJ7JwdamYAgDz+s+rVMFjt3numwzf/HckM8pak=
 google.golang.org/protobuf v0.0.0-20200109180630-ec00e32a8dfd/go.mod h1:DFci5gLYBciE7Vtevhsrf46CRTquxDuWsQurQQe4oz8=
 google.golang.org/protobuf v0.0.0-20200221191635-4d8936d0db64/go.mod h1:kwYJMbMJ01Woi6D6+Kah6886xMZcty6N08ah7+eCXa0=
 google.golang.org/protobuf v0.0.0-20200228230310-ab0ca4ff8a60/go.mod h1:cfTl7dwQJ+fmap5saPgwCLgHXTUD7jkjRqWcaiX5VyM=