Bump github.com/grpc-ecosystem/grpc-gateway/v2 in /otlp

Bumps [github.com/grpc-ecosystem/grpc-gateway/v2](https://github.com/grpc-ecosystem/grpc-gateway) from 2.19.1 to 2.20.0.
- [Release notes](https://github.com/grpc-ecosystem/grpc-gateway/releases)
- [Changelog](https://github.com/grpc-ecosystem/grpc-gateway/blob/main/.goreleaser.yml)
- [Commits](grpc-ecosystem/grpc-gateway@v2.19.1...v2.20.0)

---
updated-dependencies:
- dependency-name: github.com/grpc-ecosystem/grpc-gateway/v2
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

otlp/go.mod

@@ -3,15 +3,15 @@ module go.opentelemetry.io/proto/otlp
 go 1.17
 
 require (
-	github.com/grpc-ecosystem/grpc-gateway/v2 v2.19.1
-	google.golang.org/grpc v1.63.2
+	github.com/grpc-ecosystem/grpc-gateway/v2 v2.20.0
+	google.golang.org/grpc v1.64.0
 	google.golang.org/protobuf v1.34.1
 )
 
 require (
 	golang.org/x/net v0.23.0 // indirect
 	golang.org/x/sys v0.18.0 // indirect
-	golang.org/x/text v0.14.0 // indirect
-	google.golang.org/genproto/googleapis/api v0.0.0-20240227224415-6ceb2ff114de // indirect
-	google.golang.org/genproto/googleapis/rpc v0.0.0-20240227224415-6ceb2ff114de // indirect
+	golang.org/x/text v0.15.0 // indirect
+	google.golang.org/genproto/googleapis/api v0.0.0-20240513163218-0867130af1f8 // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20240513163218-0867130af1f8 // indirect
 )