ci: replace unmaintained rinchsan/renovate-config-validator with npx renovate-config-validator

Signed-off-by: Tom Hayward <thayward@infoblox.com>

Author: kd7lxl

.github/workflows/renovate-config-validator.yml

@@ -13,4 +13,4 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v6
       - name: Validate
-        uses: rinchsan/renovate-config-validator@v0.2.0
+        run: npx --yes --package renovate -- renovate-config-validator