Remove feature components that activate features of dev-dependencies

For example, syn has a feature `test` that activates the `all-features` feature of the dev-dependency `syn-test-suite`: ```toml [features] test = ["syn-test-suite/all-features"] [dev-dependencies.syn-test-suite] version = "0" ``` We don't store the dev-dependencies in the index which causes Cargo to complain when fetching `syn` because the feature refers to a dependency that doesn't exist.