github: bump upload-artifact to v4

Signed-off-by: Álvaro Fernández Rojas <[email protected]>

Author: Noltari

.github/workflows/ci.yml

@@ -28,7 +28,7 @@ jobs:
           make -C build
 
       - name: 'Upload binary'
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: pico-uart-bridge.uf2
           path: build/uart_bridge.uf2