Bump upload- and download-artifact to v4 (#3798)

Author: reakaleek

.github/workflows/stash/action.yml

@@ -17,7 +17,7 @@ runs:
       shell: bash
 
     - name: Upload stash
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
         name: ${{ inputs.name }}
         path: ${{ runner.temp }}/${{ inputs.name }}.tar.zst

.github/workflows/unstash/action.yml

@@ -13,7 +13,7 @@ runs:
   using: "composite"
   steps:
     - name: Download stash
-      uses: actions/download-artifact@v3
+      uses: actions/download-artifact@v4
       with:
         name: ${{ inputs.name }}
         path: ${{ runner.temp }}