ci: upgrade actions/upload-artifact from v3 to v4

v3 is deprecated and auto-failing since April 2024:
https://github.blog/changelog/2024-04-16-deprecation-notice-v3-of-the-artifact-actions/

This was blocking all PR checks on Windows.

Author: TimeToBuildBob

.github/workflows/build.yml

@@ -51,7 +51,7 @@ jobs:
       run: |
           dist/aw-watcher-window/aw-watcher-window --help
     - name: Upload package
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
         name: aw-watcher-window-${{ runner.os }}-py${{ matrix.python_version }}
         path: dist/aw-watcher-window