Exclude default winmd files from windows-metadata crate (#2060)

Author: kennykerr

crates/libs/metadata/Cargo.toml

@@ -6,6 +6,7 @@ edition = "2018"
 license = "MIT OR Apache-2.0"
 description = "Code gen support for the windows crate"
 repository = "https://github.com/microsoft/windows-rs"
+exclude = ["/default"]
 
 [package.metadata.docs.rs]
 default-target = "x86_64-pc-windows-msvc"