deps: bump google.golang.org/grpc from 1.23.1 to 1.24.0 (#4021)

Bumps [google.golang.org/grpc](https://github.com/grpc/grpc-go) from 1.23.1 to 1.24.0.
- [Release notes](https://github.com/grpc/grpc-go/releases)
- [Commits](https://github.com/grpc/grpc-go/compare/v1.23.1...v1.24.0)

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

go.mod

@@ -29,5 +29,5 @@ require (
 	github.com/tendermint/tm-db v0.2.0
 	golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2
 	golang.org/x/net v0.0.0-20190628185345-da137c7871d7
-	google.golang.org/grpc v1.23.1
+	google.golang.org/grpc v1.24.0
 )

go.sum

@@ -240,6 +240,8 @@ google.golang.org/grpc v1.23.0 h1:AzbTB6ux+okLTzP8Ru1Xs41C303zdcfEht7MQnYJt5A=
 google.golang.org/grpc v1.23.0/go.mod h1:Y5yQAOtifL1yxbo5wqy6BxZv8vAUGQwXBOALyacEbxg=
 google.golang.org/grpc v1.23.1 h1:q4XQuHFC6I28BKZpo6IYyb3mNO+l7lSOxRuYTCiDfXk=
 google.golang.org/grpc v1.23.1/go.mod h1:Y5yQAOtifL1yxbo5wqy6BxZv8vAUGQwXBOALyacEbxg=
+google.golang.org/grpc v1.24.0 h1:vb/1TCsVn3DcJlQ0Gs1yB1pKI6Do2/QNwxdKqmc/b0s=
+google.golang.org/grpc v1.24.0/go.mod h1:XDChyiUovWa60DnaeDeZmSW86xtLtjtZbwvSiRnRtcA=
 gopkg.in/alecthomas/kingpin.v2 v2.2.6/go.mod h1:FMv+mEhP44yOT+4EoQTLFTRgOQ1FBLkstjWtayDeSgw=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=