Only build, but don't run tests in MSRV CI (#2558)

* Only build, but don't run tests in MSRV CI

Since the MSRV of development dependencies can easily be bumped without it affecting the MSRV of the published version of `winit`

* Run clippy on stable Rust instead of MSRV Rust

clippy inspects the `rust-version` field, and only suggests changes that conform to that.

src/platform_impl/web/window.rs

@@ -249,7 +249,7 @@ impl Window {
         } else {
             self.canvas
                 .borrow()
-                .set_attribute("cursor", *self.previous_pointer.borrow());
+                .set_attribute("cursor", &self.previous_pointer.borrow());
         }
     }