chore(deps): update actions/setup-go action to v6

Author: renovate[bot]

.github/workflows/pr-auditor.yml

@@ -13,7 +13,7 @@ jobs:
         with:
           repository: 'sourcegraph/devx-service'
           token: ${{ secrets.PR_AUDITOR_TOKEN }}
-      - uses: actions/setup-go@v4
+      - uses: actions/setup-go@v6
         with: { go-version: '1.22' }
 
       - run: 'go run ./cmd/pr-auditor'