Fix outdated lint warning about inner attribute

It suggested adding a semicolon instead of the new syntax using an exclamation
mark.
auto merge of #13430 : aepsil0n/rust/fix_crate_attr_lint, r=brson

It suggested adding a semicolon instead of the new syntax using an exclamation mark. This lint misled me and made me run into another warning about the new syntax so I fixed it.