add features needed to build the examples

Author: TommyCpp

examples/tracing-grpc/Cargo.toml

@@ -19,7 +19,7 @@ opentelemetry_sdk = { path = "../../opentelemetry-sdk", features = ["rt-tokio"]
 opentelemetry-stdout = { path = "../../opentelemetry-stdout", features = ["trace"] }
 prost = { workspace = true }
 tokio = { workspace = true, features = ["full"] }
-tonic = { workspace = true }
+tonic = { workspace = true, features = ["codegen", "transport", "prost"] }
 serde_json = { workspace = true }
 
 [build-dependencies]