chore(deps): bump google.golang.org/grpc in /t/assets/grpc

Bumps [google.golang.org/grpc](https://github.com/grpc/grpc-go) from 1.53.0 to 1.56.3.
- [Release notes](https://github.com/grpc/grpc-go/releases)
- [Commits](grpc/grpc-go@v1.53.0...v1.56.3)

---
updated-dependencies:
- dependency-name: google.golang.org/grpc
  dependency-version: 1.56.3
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

t/assets/grpc/go.mod

@@ -3,6 +3,6 @@ module apisix.apache.org/plugin/grpc-web
 go 1.16
 
 require (
-	github.com/golang/protobuf v1.5.2
-	google.golang.org/grpc v1.53.0
+	github.com/golang/protobuf v1.5.3
+	google.golang.org/grpc v1.56.3
 )