CI: run cargo doc with --no-deps (#74)

We only care that `rustls-rustcrypto` documentation builds successfully,
so avoid documenting dependencies to improve build times

Author: tarcieri

.github/workflows/rustls-rustcrypto.yml

@@ -34,7 +34,7 @@ jobs:
       - uses: dtolnay/rust-toolchain@master
         with:
           toolchain: stable
-      - run: cargo doc --all-features
+      - run: cargo doc --all-features --no-deps
 
   rustfmt:
     runs-on: ubuntu-latest