Add sparse-checkout to kubernetes-json-schema checkout (#493)

Author: pdabelf5

.github/workflows/sync-chart.yml

@@ -41,6 +41,8 @@ jobs:
           repository: nginxinc/kubernetes-json-schema
           path: schemas
           token: ${{ secrets.NGINX_PAT }}
+          sparse-checkout: |
+            ${{ inputs.k8s_version}}
 
       - name: Setup Helm
         uses: azure/setup-helm@b9e51907a09c216f16ebe8536097933489208112 # v4.3.0