ci: Switch to download-artifact v4

See https://github.com/actions/upload-artifact?tab=readme-ov-file#v4---whats-new
from what I can tell, we're not affected by the breaking changes.

The v3 action will stop working on January 30th:
https://github.blog/changelog/2024-04-16-deprecation-notice-v3-of-the-artifact-actions/

Author: The-Compiler

.github/workflows/deploy.yml

@@ -30,7 +30,7 @@ jobs:
     - uses: actions/checkout@v3
 
     - name: Download Package
-      uses: actions/download-artifact@v3
+      uses: actions/download-artifact@v4
       with:
         name: Packages
         path: dist

.github/workflows/test.yml

@@ -45,7 +45,7 @@ jobs:
         python-version: ${{ matrix.python-version }}
 
     - name: Download Package
-      uses: actions/download-artifact@v3
+      uses: actions/download-artifact@v4
       with:
         name: Packages
         path: dist