CI: Only MSRV-test published ash and ash-window crates (#677)

`bytemuck` recently bumped its MSRV to 1.60 which is incompatible with
what we're currently advertising.  Fortunately this doesn't affect MSRV
of the publicly published crates, but only `dev-dependencies` inside
`ash-window` via `winit`: make sure the CI doesn't reject this.

.github/workflows/ci.yml

@@ -27,7 +27,7 @@ jobs:
       - uses: actions-rs/cargo@v1
         with:
           command: check
-          args: --workspace --all-targets --all-features
+          args: -p ash -p ash-window --all-features
 
   generated:
     name: Generated