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

@@ -4,6 +4,7 @@ on:
   push:
     paths:
       - renovate.json
+      - .github/workflows/renovate-config-validator.yml
 
 jobs:
   validate:
@@ -13,4 +14,4 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v6
       - name: Validate
-        uses: rinchsan/renovate-config-validator@v0.2.1
+        run: npx --yes --package renovate -- renovate-config-validator