CI: Update to download-artifact/v8

Author: sourcefrog

.github/workflows/tests.yml

@@ -240,7 +240,7 @@ jobs:
         with:
           tool: nextest
       - name: Download cargo-mutants binary
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v8
         with:
           name: cargo-mutants-linux
       - name: Install cargo-mutants binary
@@ -284,7 +284,7 @@ jobs:
         with:
           tool: nextest
       - name: Download cargo-mutants binary
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v8
         with:
           name: cargo-mutants-linux
       - name: Install cargo-mutants binary
@@ -332,7 +332,7 @@ jobs:
           rustflags = ["-C", "link-arg=--ld-path=wild"]
           EOF
       - name: Download cargo-mutants binary
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v8
         with:
           name: cargo-mutants-linux
       - name: Install cargo-mutants binary