Bump codecov-action to v6 for Node 24 support

v6.0.0 pins github-script@v8 which runs natively on Node 24,
resolving the deprecation warning at the source instead of
forcing via FORCE_JAVASCRIPT_ACTIONS_TO_NODE24.

Author: emazzotta

.github/workflows/build.yml

@@ -9,7 +9,6 @@ on:
 env:
   TAG_PREFIX: emazzotta/lighthouse-badges
   BUN_VERSION: 1.3.12
-  FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: true
 
 permissions:
   id-token: write
@@ -46,7 +45,7 @@ jobs:
         run: bun run test:coverage
 
       - name: Upload Coverage to Codecov
-        uses: codecov/codecov-action@v5
+        uses: codecov/codecov-action@v6
         with:
           files: coverage/lcov.info
           token: ${{ secrets.CODECOV_TOKEN }}