[pkg-go] golang-github-opencontainers-image-spec is marked for autoremoval from testing

[Debian testing autoremoval watch]

golang-github-opencontainers-image-spec 1.0.1-1 is marked for autoremoval from testing on 2019-02-20

It (build-)depends on packages with these RC bugs:
918618: golang-github-grpc-ecosystem-grpc-gateway: golang-github-grpc-ecosystem-grpc-gateway FTBFS: github.com/grpc-ecosystem/grpc-gateway/runtime [build failed]