fix(spanner): avoid double grpc-gcp wrapping for directpath fallback#13155

rahul2393 wants to merge 2 commits intomaingoogleapis/google-cloud-java:mainfrom

directpath-fix-1-remove-double-grpc-gcp-wrapgoogleapis/google-cloud-java:directpath-fix-1-remove-double-grpc-gcp-wrapCopy head branch name to clipboard