CI: Bump {upload,download}-artifact to v4 because v3 is disallowed

Author: MarijnS95

.github/workflows/ci.yml

@@ -27,7 +27,7 @@ jobs:
     - uses: actions/checkout@v3
     - uses: hecrj/setup-rust-action@v1
     - run: cargo install --path xbuild --root .
-    - uses: actions/upload-artifact@v3
+    - uses: actions/upload-artifact@v4
       with:
         name: ${{ matrix.host }}-x
         path: bin/x${{ matrix.host == 'windows-latest' && '.exe' || '' }}
@@ -64,7 +64,7 @@ jobs:
         rust-version: stable
 
     - name: install x
-      uses: actions/download-artifact@v3
+      uses: actions/download-artifact@v4
       with:
         name: ${{ matrix.host }}-x
     - run: chmod +x ./x