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/windows/window.rs

@@ -1116,7 +1116,7 @@ unsafe fn taskbar_mark_fullscreen(handle: HWND, fullscreen: bool) {
 
         task_bar_list2 = task_bar_list2_ptr.get();
         let mark_fullscreen_window = (*(*task_bar_list2).lpVtbl).MarkFullscreenWindow;
-        mark_fullscreen_window(task_bar_list2, handle, if fullscreen { 1 } else { 0 });
+        mark_fullscreen_window(task_bar_list2, handle, fullscreen.into());
     })
 }