build(deps): bump google.golang.org/grpc from 1.35.0 to 1.39.0 (#266)

Bumps [google.golang.org/grpc](https://github.com/grpc/grpc-go) from 1.35.0 to 1.39.0.
- [Release notes](https://github.com/grpc/grpc-go/releases)
- [Commits](grpc/grpc-go@v1.35.0...v1.39.0)

---
updated-dependencies:
- dependency-name: google.golang.org/grpc
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: egonspace <woosang.son@linecorp.com>

go.mod

@@ -62,7 +62,7 @@ require (
 	golang.org/x/sys v0.0.0-20210403161142-5e06dd20ab57 // indirect
 	golang.org/x/text v0.3.5 // indirect
 	google.golang.org/genproto v0.0.0-20210114201628-6edceaf6022f
-	google.golang.org/grpc v1.35.0
+	google.golang.org/grpc v1.39.0
 	google.golang.org/protobuf v1.25.0
 	gopkg.in/check.v1 v1.0.0-20200227125254-8fa46927fb4f // indirect
 	gopkg.in/yaml.v2 v2.4.0