Update coursier/cache-action action to v8

Author: renovate[bot]

.github/workflows/ci.yml

@@ -18,7 +18,7 @@ jobs:
         with:
           java-version: ${{ matrix.java }}
       - name: Coursier cache
-        uses: coursier/cache-action@v7
+        uses: coursier/cache-action@v8
       - name: sbt ci ${{ github.ref }}
         run: ./sbt ci