envoy_build_system: remove unused build macro (#6941)
envoy_build_system: remove unused build macro (#6941)

This build macro is private (_) and unused in envoy_build_system.bzl.

Risk Level: Low
Testing: Ran bazel test //test/common/... //test/exe/...

Signed-off-by: Frank Fort <fdfbceb5ed4073410ce08fbd0f7c033bb477f889@google.com>
lizan/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy,envoyproxy/envoy,lizan/envoy,istio/envoy,istio/envoy,lizan/envoy,lyft/envoy,lyft/envoy,jrajahalme/envoy,istio/envoy,envoyproxy/envoy-wasm,jrajahalme/envoy,envoyproxy/envoy,lizan/envoy,envoyproxy/envoy,jrajahalme/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy,envoyproxy/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy-wasm,eklitzke/envoy,envoyproxy/envoy,istio/envoy,eklitzke/envoy,lyft/envoy,envoyproxy/envoy,eklitzke/envoy,envoyproxy/envoy-wasm,eklitzke/envoy,lizan/envoy,jrajahalme/envoy,istio/envoy,istio/envoy,envoyproxy/envoy-wasm,istio/envoy,lizan/envoy,envoyproxy/envoy,lyft/envoy,lyft/envoy,jrajahalme/envoy,eklitzke/envoy,jrajahalme/envoy,eklitzke/envoy,envoyproxy/envoy,envoyproxy/envoy,lyft/envoy,envoyproxy/envoy