ci: fix vitest cache path & use blacksmith runners

Author: JesusTheHun

.github/workflows/tests.yml

@@ -17,8 +17,7 @@ jobs:
       github.event_name == 'workflow_dispatch'
     timeout-minutes: 30
     runs-on:
-      group: couchbase-runners
-      labels: ubuntu-latest-m
+      labels: blacksmith-4vcpu-ubuntu-2404
     strategy:
       fail-fast: false
       matrix:
@@ -73,7 +72,7 @@ jobs:
       - name: Vitest cache
         uses: actions/cache@v4
         with:
-          path: ./node_modules/.vite/vitest/results.json
+          path: ./node_modules/.vite/results.json
           key: vitest-cache-${{ github.ref_name }}
           restore-keys: |
             vitest-cache-main